diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 15149f25703310fa42aac15fc6b43e714066c960..03e97a1479740a3fb770ee075bb4808e88683951 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -128,124 +128,123 @@
  * M1   - Same as M0
  * M17  - Enable/Power all stepper motors
  * M18  - Disable all stepper motors; same as M84
- * M20  - List SD card
- * M21  - Init SD card
- * M22  - Release SD card
- * M23  - Select SD file (M23 filename.g)
- * M24  - Start/resume SD print
- * M25  - Pause SD print
- * M26  - Set SD position in bytes (M26 S12345)
- * M27  - Report SD print status
- * M28  - Start SD write (M28 filename.g)
- * M29  - Stop SD write
- * M30  - Delete file from SD (M30 filename.g)
- * M31  - Output time since last M109 or SD card start to serial
- * M32  - Select file and start SD print (Can be used _while_ printing from SD card files):
- *        syntax "M32 /path/filename#", or "M32 S<startpos bytes> !filename#"
- *        Call gcode file : "M32 P !filename#" and return to caller file after finishing (similar to #include).
+ * M20  - List SD card. (Requires SDSUPPORT)
+ * M21  - Init SD card. (Requires SDSUPPORT)
+ * M22  - Release SD card. (Requires SDSUPPORT)
+ * M23  - Select SD file: "M23 /path/file.gco". (Requires SDSUPPORT)
+ * M24  - Start/resume SD print. (Requires SDSUPPORT)
+ * M25  - Pause SD print. (Requires SDSUPPORT)
+ * M26  - Set SD position in bytes: "M26 S12345". (Requires SDSUPPORT)
+ * M27  - Report SD print status. (Requires SDSUPPORT)
+ * M28  - Start SD write: "M28 /path/file.gco". (Requires SDSUPPORT)
+ * M29  - Stop SD write. (Requires SDSUPPORT)
+ * M30  - Delete file from SD: "M30 /path/file.gco"
+ * M31  - Report time since last M109 or SD card start to serial.
+ * M32  - Select file and start SD print: "M32 [S<bytepos>] !/path/file.gco#". (Requires SDSUPPORT)
+ *        Use P to run other files as sub-programs: "M32 P !filename#"
  *        The '#' is necessary when calling from within sd files, as it stops buffer prereading
- * M33  - Get the longname version of a path
- * M42  - Change pin status via gcode Use M42 Px Sy to set pin x to value y, when omitting Px the onboard led will be used.
- * M48  - Measure Z_Probe repeatability. M48 [P # of points] [X position] [Y position] [V_erboseness #] [E_ngage Probe] [L # of legs of travel]
- * M75  - Start the print job timer
- * M76  - Pause the print job timer
- * M77  - Stop the print job timer
- * M78  - Show statistical information about the print jobs
- * M80  - Turn on Power Supply
- * M81  - Turn off Power Supply
- * M82  - Set E codes absolute (default)
- * M83  - Set E codes relative while in Absolute Coordinates (G90) mode
- * M84  - Disable steppers until next move,
- *        or use S<seconds> to specify an inactivity timeout, after which the steppers will be disabled.  S0 to disable the timeout.
+ * M33  - Get the longname version of a path. (Requires LONG_FILENAME_HOST_SUPPORT)
+ * M42  - Change pin status via gcode: M42 P<pin> S<value>. LED pin assumed if P is omitted.
+ * M48  - Measure Z Probe repeatability: M48 P<points> X<pos> Y<pos> V<level> E<engage> L<legs>. (Requires Z_MIN_PROBE_REPEATABILITY_TEST)
+ * M75  - Start the print job timer.
+ * M76  - Pause the print job timer.
+ * M77  - Stop the print job timer.
+ * M78  - Show statistical information about the print jobs. (Requires PRINTCOUNTER)
+ * M80  - Turn on Power Supply. (Requires POWER_SUPPLY)
+ * M81  - Turn off Power Supply. (Requires POWER_SUPPLY)
+ * M82  - Set E codes absolute (default).
+ * M83  - Set E codes relative while in Absolute (G90) mode.
+ * M84  - Disable steppers until next move, or use S<seconds> to specify an idle
+ *        duration after which steppers should turn off. S0 disables the timeout.
  * M85  - Set inactivity shutdown timer with parameter S<seconds>. To disable set zero (default)
- * M92  - Set planner.axis_steps_per_mm - same syntax as G92
- * M104 - Set extruder target temp
- * M105 - Read current temp
- * M106 - Fan on
- * M107 - Fan off
- * M108 - Stop the waiting for heaters in M109, M190, M303. Does not affect the target temperature.
+ * M92  - Set planner.axis_steps_per_mm for one or more axes.
+ * M104 - Set extruder target temp.
+ * M105 - Report current temperatures.
+ * M106 - Fan on.
+ * M107 - Fan off.
+ * M108 - Break out of heating loops (M109, M190, M303). With no controller, breaks out of M0/M1. (Requires EMERGENCY_PARSER)
  * M109 - Sxxx Wait for extruder current temp to reach target temp. Waits only when heating
  *        Rxxx Wait for extruder current temp to reach target temp. Waits when heating and cooling
  *        IF AUTOTEMP is enabled, S<mintemp> B<maxtemp> F<factor>. Exit autotemp by any M109 without F
- * M110 - Set the current line number
- * M111 - Set debug flags with S<mask>. See flag bits defined in enum.h.
- * M112 - Emergency stop
- * M113 - Get or set the timeout interval for Host Keepalive "busy" messages
- * M114 - Output current position to serial port
- * M115 - Capabilities string
- * M117 - Display a message on the controller screen
- * M119 - Output Endstop status to serial port
- * M120 - Enable endstop detection
- * M121 - Disable endstop detection
- * M126 - Solenoid Air Valve Open (BariCUDA support by jmil)
- * M127 - Solenoid Air Valve Closed (BariCUDA vent to atmospheric pressure by jmil)
- * M128 - EtoP Open (BariCUDA EtoP = electricity to air pressure transducer by jmil)
- * M129 - EtoP Closed (BariCUDA EtoP = electricity to air pressure transducer by jmil)
- * M140 - Set bed target temp
- * M145 - Set the heatup state H<hotend> B<bed> F<fan speed> for S<material> (0=PLA, 1=ABS)
- * M149 - Set temperature units
- * M150 - Set BlinkM Color Output R: Red<0-255> U(!): Green<0-255> B: Blue<0-255> over i2c, G for green does not work.
- * M163 - Set a single proportion for a mixing extruder. Requires MIXING_EXTRUDER.
- * M164 - Save the mix as a virtual extruder. Requires MIXING_EXTRUDER and MIXING_VIRTUAL_TOOLS.
- * M165 - Set the proportions for a mixing extruder. Use parameters ABCDHI to set the mixing factors. Requires MIXING_EXTRUDER.
- * M190 - Sxxx Wait for bed current temp to reach target temp. Waits only when heating
- *        Rxxx Wait for bed current temp to reach target temp. Waits when heating and cooling
+ * M110 - Set the current line number. (Used by host printing)
+ * M111 - Set debug flags: "M111 S<flagbits>". See flag bits defined in enum.h.
+ * M112 - Emergency stop.
+ * M113 - Get or set the timeout interval for Host Keepalive "busy" messages. (Requires HOST_KEEPALIVE_FEATURE)
+ * M114 - Report current position.
+ * M115 - Report capabilities.
+ * M117 - Display a message on the controller screen. (Requires an LCD)
+ * M119 - Report endstops status.
+ * M120 - Enable endstops detection.
+ * M121 - Disable endstops detection.
+ * M126 - Solenoid Air Valve Open. (Requires BARICUDA)
+ * M127 - Solenoid Air Valve Closed. (Requires BARICUDA)
+ * M128 - EtoP Open. (Requires BARICUDA)
+ * M129 - EtoP Closed. (Requires BARICUDA)
+ * M140 - Set bed target temp. S<temp>
+ * M145 - Set heatup values for materials on the LCD. H<hotend> B<bed> F<fan speed> for S<material> (0=PLA, 1=ABS)
+ * M149 - Set temperature units. (Requires TEMPERATURE_UNITS_SUPPORT)
+ * M150 - Set BlinkM Color R<red> U<green> B<blue>. Values 0-255. (Requires BLINKM)
+ * M163 - Set a single proportion for a mixing extruder. (Requires MIXING_EXTRUDER)
+ * M164 - Save the mix as a virtual extruder. (Requires MIXING_EXTRUDER and MIXING_VIRTUAL_TOOLS)
+ * M165 - Set the proportions for a mixing extruder. Use parameters ABCDHI to set the mixing factors. (Requires MIXING_EXTRUDER)
+ * M190 - Sxxx Wait for bed current temp to reach target temp. ** Waits only when heating! **
+ *        Rxxx Wait for bed current temp to reach target temp. ** Waits for heating or cooling. **
  * M200 - Set filament diameter, D<diameter>, setting E axis units to cubic. (Use S0 to revert to linear units.)
- * M201 - Set max acceleration in units/s^2 for print moves (M201 X1000 Y1000)
- * M202 - Set max acceleration in units/s^2 for travel moves (M202 X1000 Y1000) Unused in Marlin!!
- * M203 - Set maximum feedrate that your machine can sustain (M203 X200 Y200 Z300 E10000) in units/sec
- * M204 - Set default acceleration: P for Printing moves, R for Retract only (no X, Y, Z) moves and T for Travel (non printing) moves (ex. M204 P800 T3000 R9000) in units/sec^2
+ * M201 - Set max acceleration in units/s^2 for print moves: "M201 X<accel> Y<accel> Z<accel> E<accel>"
+ * M202 - Set max acceleration in units/s^2 for travel moves: "M202 X<accel> Y<accel> Z<accel> E<accel>" ** UNUSED IN MARLIN! **
+ * M203 - Set maximum feedrate: "M203 X<fr> Y<fr> Z<fr> E<fr>" in units/sec.
+ * M204 - Set default acceleration in units/sec^2: P<printing> R<extruder_only> T<travel>
  * M205 - Set advanced settings. Current units apply:
             S<print> T<travel> minimum speeds
             B<minimum segment time>
             X<max xy jerk>, Z<max Z jerk>, E<max E jerk>
- * M206 - Set additional homing offset
- * M207 - Set Retract Length: S<length>, Feedrate: F<units/min>, and Z lift: Z<distance>
- * M208 - Set Recover (unretract) Additional (!) Length: S<length> and Feedrate: F<units/min>
- * M209 - Turn Automatic Retract Detection on/off: S<bool> (For slicers that don't support G10/11).
+ * M206 - Set additional homing offset.
+ * M207 - Set Retract Length: S<length>, Feedrate: F<units/min>, and Z lift: Z<distance>. (Requires FWRETRACT)
+ * M208 - Set Recover (unretract) Additional (!) Length: S<length> and Feedrate: F<units/min>. (Requires FWRETRACT)
+ * M209 - Turn Automatic Retract Detection on/off: S<0|1> (For slicers that don't support G10/11). (Requires FWRETRACT)
           Every normal extrude-only move will be classified as retract depending on the direction.
- * M211 - Enable, Disable, and/or Report software endstops: [S<bool>]
- * M218 - Set a tool offset: T<index> X<offset> Y<offset>
- * M220 - Set Feedrate Percentage: S<percent> ("FR" on your LCD)
- * M221 - Set Flow Percentage: S<percent>
- * M226 - Wait until the specified pin reaches the state required: P<pin number> S<pin state>
- * M240 - Trigger a camera to take a photograph
- * M250 - Set LCD contrast C<contrast value> (value 0..63)
- * M280 - Set servo position absolute. P: servo index, S: angle or microseconds
+ * M211 - Enable, Disable, and/or Report software endstops: S<0|1>
+ * M218 - Set a tool offset: "M218 T<index> X<offset> Y<offset>". (Requires 2 or more extruders)
+ * M220 - Set Feedrate Percentage: "M220 S<percent>" (i.e., "FR" on the LCD)
+ * M221 - Set Flow Percentage: "M221 S<percent>"
+ * M226 - Wait until a pin is in a given state: "M226 P<pin> S<state>"
+ * M240 - Trigger a camera to take a photograph. (Requires CHDK or PHOTOGRAPH_PIN)
+ * M250 - Set LCD contrast: "M250 C<contrast>" (0-63). (Requires LCD support)
+ * M280 - Set servo position absolute: "M280 P<index> S<angle|µs>". (Requires servos)
  * M300 - Play beep sound S<frequency Hz> P<duration ms>
- * M301 - Set PID parameters P I and D
- * M302 - Allow cold extrudes, or set the minimum extrude S<temperature>.
- * M303 - PID relay autotune S<temperature> sets the target temperature. (default target temperature = 150C)
- * M304 - Set bed PID parameters P I and D
- * M380 - Activate solenoid on active extruder
- * M381 - Disable all solenoids
- * M400 - Finish all moves
- * M401 - Lower Z probe if present
- * M402 - Raise Z probe if present
- * M404 - Display or set the Nominal Filament Width: [ N<diameter> ]
- * M405 - Enable Filament Sensor extrusion control. Optional delay between sensor and extruder: D<cm>
- * M406 - Disable Filament Sensor extrusion control
- * M407 - Display measured filament diameter in millimeters
- * M410 - Quickstop. Abort all the planned moves
- * M420 - Enable/Disable Mesh Leveling (with current values) S1=enable S0=disable
- * M421 - Set a single Z coordinate in the Mesh Leveling grid. X<units> Y<units> Z<units>
- * M428 - Set the home_offset logically based on the current_position
- * M500 - Store parameters in EEPROM
- * M501 - Read parameters from EEPROM (if you need reset them after you changed them temporarily).
- * M502 - Revert to the default "factory settings". You still need to store them in EEPROM afterwards if you want to.
- * M503 - Print the current settings (from memory not from EEPROM). Use S0 to leave off headings.
- * M540 - Use S[0|1] to enable or disable the stop SD card print on endstop hit (requires ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
- * M600 - Pause for filament change X[pos] Y[pos] Z[relative lift] E[initial retract] L[later retract distance for removal]
- * M665 - Set delta configurations: L<diagonal rod> R<delta radius> S<segments/s>
- * M666 - Set delta endstop adjustment
- * M605 - Set dual x-carriage movement mode: S<mode> [ X<duplication x-offset> R<duplication temp offset> ]
- * M851 - Set Z probe's Z offset in current units. (Negative values apply to probes that extend below the nozzle.)
- * M907 - Set digital trimpot motor current using axis codes.
- * M908 - Control digital trimpot directly.
- * M909 - DAC_STEPPER_CURRENT: Print digipot/DAC current value
- * M910 - DAC_STEPPER_CURRENT: Commit digipot/DAC value to external EEPROM via I2C
- * M350 - Set microstepping mode.
- * M351 - Toggle MS1 MS2 pins directly.
+ * M301 - Set PID parameters P I and D. (Requires PIDTEMP)
+ * M302 - Allow cold extrudes, or set the minimum extrude S<temperature>. (Requires PREVENT_COLD_EXTRUSION)
+ * M303 - PID relay autotune S<temperature> sets the target temperature. Default 150C. (Requires PIDTEMP)
+ * M304 - Set bed PID parameters P I and D. (Requires PIDTEMPBED)
+ * M380 - Activate solenoid on active extruder. (Requires EXT_SOLENOID)
+ * M381 - Disable all solenoids. (Requires EXT_SOLENOID)
+ * M400 - Finish all moves.
+ * M401 - Lower Z probe. (Requires a probe)
+ * M402 - Raise Z probe. (Requires a probe)
+ * M404 - Display or set the Nominal Filament Width: "W<diameter>". (Requires FILAMENT_WIDTH_SENSOR)
+ * M405 - Enable Filament Sensor flow control. "M405 D<delay_cm>". (Requires FILAMENT_WIDTH_SENSOR)
+ * M406 - Disable Filament Sensor flow control. (Requires FILAMENT_WIDTH_SENSOR)
+ * M407 - Display measured filament diameter in millimeters. (Requires FILAMENT_WIDTH_SENSOR)
+ * M410 - Quickstop. Abort all planned moves.
+ * M420 - Enable/Disable Mesh Leveling (with current values) S1=enable S0=disable (Requires MESH_BED_LEVELING)
+ * M421 - Set a single Z coordinate in the Mesh Leveling grid. X<units> Y<units> Z<units> (Requires MESH_BED_LEVELING)
+ * M428 - Set the home_offset based on the current_position. Nearest edge applies.
+ * M500 - Store parameters in EEPROM. (Requires EEPROM_SETTINGS)
+ * M501 - Restore parameters from EEPROM. (Requires EEPROM_SETTINGS)
+ * M502 - Revert to the default "factory settings". ** Does not write them to EEPROM! **
+ * M503 - Print the current settings (in memory): "M503 S<verbose>". S0 specifies compact output.
+ * M540 - Enable/disable SD card abort on endstop hit: "M540 S<state>". (Requires ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED)
+ * M600 - Pause for filament change: "M600 X<pos> Y<pos> Z<raise> E<first_retract> L<later_retract>". (Requires FILAMENT_CHANGE_FEATURE)
+ * M665 - Set delta configurations: "M665 L<diagonal rod> R<delta radius> S<segments/s>" (Requires DELTA)
+ * M666 - Set delta endstop adjustment. (Requires DELTA)
+ * M605 - Set dual x-carriage movement mode: "M605 S<mode> [X<x_offset>] [R<temp_offset>]". (Requires DUAL_X_CARRIAGE)
+ * M851 - Set Z probe's Z offset in current units. (Negative = below the nozzle.)
+ * M907 - Set digital trimpot motor current using axis codes. (Requires a board with digital trimpots)
+ * M908 - Control digital trimpot directly. (Requires DAC_STEPPER_CURRENT or DIGIPOTSS_PIN)
+ * M909 - Print digipot/DAC current value. (Requires DAC_STEPPER_CURRENT)
+ * M910 - Commit digipot/DAC value to external EEPROM via I2C. (Requires DAC_STEPPER_CURRENT)
+ * M350 - Set microstepping mode. (Requires digital microstepping pins.)
+ * M351 - Toggle MS1 MS2 pins directly. (Requires digital microstepping pins.)
  *
  * ************ SCARA Specific - This can change to suit future G-code regulations
  * M360 - SCARA calibration: Move to cal-position ThetaA (0 deg calibration)
@@ -256,13 +255,13 @@
  * ************* SCARA End ***************
  *
  * ************ Custom codes - This can change to suit future G-code regulations
- * M100 - Watch Free Memory (For Debugging Only)
- * M928 - Start SD logging (M928 filename.g) - ended by M29
+ * M100 - Watch Free Memory (For Debugging). (Requires M100_FREE_MEMORY_WATCHER)
+ * M928 - Start SD logging: "M928 filename.gco". Stop with M29. (Requires SDSUPPORT)
  * M999 - Restart after being stopped by error
  *
  * "T" Codes
  *
- * T0-T3 - Select a tool by index (usually an extruder) [ F<units/min> ]
+ * T0-T3 - Select an extruder (tool) by index: "T<n> F<units/min>"
  *
  */