Option to set manual Babystepping distance in mm (#18503)

Co-authored-by: Scott Lahteine <github@thinkyhead.com>

Marlin/Configuration_adv.h

   //#define BABYSTEP_WITHOUT_HOMING
   //#define BABYSTEP_XY                     // Also enable X/Y Babystepping. Not supported on DELTA!
   #define BABYSTEP_INVERT_Z false           // Change if Z babysteps should go the other way
-  #define BABYSTEP_MULTIPLICATOR_Z  1       // Babysteps are very small. Increase for faster motion.
-  #define BABYSTEP_MULTIPLICATOR_XY 1
+  //#define BABYSTEP_MILLIMETER_UNITS       // Specify BABYSTEP_MULTIPLICATOR_(XY|Z) in mm instead of micro-steps
+  #define BABYSTEP_MULTIPLICATOR_Z  1       // (steps or mm) Steps or millimeter distance for each Z babystep
+  #define BABYSTEP_MULTIPLICATOR_XY 1       // (steps or mm) Steps or millimeter distance for each XY babystep
 
   //#define DOUBLECLICK_FOR_Z_BABYSTEPPING  // Double-click on the Status Screen for Z Babystepping.
   #if ENABLED(DOUBLECLICK_FOR_Z_BABYSTEPPING)

Marlin/src/lcd/menu/menu.cpp

     ui.defer_status_screen();
     const bool do_probe = DISABLED(BABYSTEP_HOTEND_Z_OFFSET) || active_extruder == 0;
     if (ui.encoderPosition) {
-      const int16_t babystep_increment = int16_t(ui.encoderPosition) * (BABYSTEP_MULTIPLICATOR_Z);
+      const int16_t babystep_increment = int16_t(ui.encoderPosition) * (BABYSTEP_SIZE_Z);
       ui.encoderPosition = 0;
 
       const float diff = planner.steps_to_mm[Z_AXIS] * babystep_increment,

Marlin/src/lcd/menu/menu.h

   #else
     void lcd_babystep_z();
   #endif
+
+  #if ENABLED(BABYSTEP_MILLIMETER_UNITS)
+    #define BABYSTEP_SIZE_X int32_t((BABYSTEP_MULTIPLICATOR_XY) * planner.settings.axis_steps_per_mm[X_AXIS])
+    #define BABYSTEP_SIZE_Y int32_t((BABYSTEP_MULTIPLICATOR_XY) * planner.settings.axis_steps_per_mm[Y_AXIS])
+    #define BABYSTEP_SIZE_Z int32_t((BABYSTEP_MULTIPLICATOR_Z)  * planner.settings.axis_steps_per_mm[Z_AXIS])
+  #else
+    #define BABYSTEP_SIZE_X BABYSTEP_MULTIPLICATOR_XY
+    #define BABYSTEP_SIZE_Y BABYSTEP_MULTIPLICATOR_XY
+    #define BABYSTEP_SIZE_Z BABYSTEP_MULTIPLICATOR_Z
+  #endif
+
 #endif
 
 #if ENABLED(POWER_LOSS_RECOVERY)

Marlin/src/lcd/menu/menu_tune.cpp

     if (ui.encoderPosition) {
       const int16_t steps = int16_t(ui.encoderPosition) * (
         #if ENABLED(BABYSTEP_XY)
-          axis != Z_AXIS ? BABYSTEP_MULTIPLICATOR_XY :
+          axis == X_AXIS ? BABYSTEP_SIZE_X :
+          axis == Y_AXIS ? BABYSTEP_SIZE_Y :
         #endif
-        BABYSTEP_MULTIPLICATOR_Z
+        BABYSTEP_SIZE_Z
       );
       ui.encoderPosition = 0;
       ui.refresh(LCDVIEW_REDRAW_NOW);