Fix manual move with MKS H43 (#21511)

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

Marlin/src/gcode/gcode.cpp

@@ -977,6 +977,10 @@ void GcodeSuite::process_parsed_command(const bool no_ok/*=false*/) {
         case 1001: M1001(); break;                                // M1001: [INTERNAL] Handle SD completion
       #endif
 
+      #if ENABLED(DGUS_LCD_UI_MKS)
+        case 1002: M1002(); break;                                // M1002: [INTERNAL] Tool-change and Relative E Move
+      #endif
+
       #if ENABLED(MAX7219_GCODE)
         case 7219: M7219(); break;                                // M7219: Set LEDs, columns, and rows
       #endif

Marlin/src/gcode/gcode.h

@@ -1069,6 +1069,10 @@ private:
     static void M1001();
   #endif
 
+  #if ENABLED(DGUS_LCD_UI_MKS)
+    static void M1002();
+  #endif
+
   #if ENABLED(MAX7219_GCODE)
     static void M7219();
   #endif