Added Menu entry for Case light

Marlin/Marlin_main.cpp

   ;
 #endif
 
+#if ENABLED(ULTIPANEL) && HAS_CASE_LIGHT
+  bool case_light_on =
+    #if ENABLED(CASE_LIGHT_DEFAULT_ON)
+      true
+    #else
+      false
+    #endif
+  ;
+#endif
+
 #if ENABLED(DELTA)
 
   #define SIN_60 0.8660254037844386
    *   P<byte>  Set case light brightness (PWM pin required)
    */
   inline void gcode_M355() {
-    static bool case_light_on
-      #if ENABLED(CASE_LIGHT_DEFAULT_ON)
-        = true
-      #endif
-    ;
     static uint8_t case_light_brightness = 255;
     if (code_seen('P')) case_light_brightness = code_value_byte();
     if (code_seen('S')) {

Marlin/language_en.h

 #ifndef MSG_INFO_PROTOCOL
   #define MSG_INFO_PROTOCOL                   "Protocol"
 #endif
+#ifndef MSG_LIGHTS_ON
+  #define MSG_LIGHTS_ON                       "Case light on"
+#endif
+#ifndef MSG_LIGHTS_OFF
+  #define MSG_LIGHTS_OFF                      "Case light off"
+#endif
 
 #if LCD_WIDTH >= 20
   #ifndef MSG_INFO_PRINT_COUNT

Marlin/ultralcd.cpp

   #if HAS_POWER_SWITCH
     extern bool powersupply;
   #endif
+  #if HAS_CASE_LIGHT
+    extern bool case_light_on;
+  #endif
   const float manual_feedrate_mm_m[] = MANUAL_FEEDRATE;
   static void lcd_main_menu();
   static void lcd_tune_menu();
     START_MENU();
     MENU_BACK(MSG_WATCH);
 
+    //
+    // Switch case light on/off
+    //
+    #if HAS_CASE_LIGHT && ENABLED(MENU_ITEM_CASE_LIGHT)
+      if (case_light_on == 0)
+        MENU_ITEM(gcode, MSG_LIGHTS_ON, PSTR("M355 S1"));
+      else
+        MENU_ITEM(gcode, MSG_LIGHTS_OFF, PSTR("M355 S0"));
+    #endif
+
     #if ENABLED(BLTOUCH)
       if (!endstops.z_probe_enabled && TEST_BLTOUCH())
         MENU_ITEM(gcode, MSG_BLTOUCH_RESET, PSTR("M280 P" STRINGIFY(Z_ENDSTOP_SERVO_NR) " S" STRINGIFY(BLTOUCH_RESET)));
 
     static void lcd_dac_menu() {
       dac_driver_getValues();
-      START_MENU();    
+      START_MENU();
       MENU_BACK(MSG_CONTROL);
       MENU_ITEM_EDIT_CALLBACK(int3, MSG_X " " MSG_DAC_PERCENT, &driverPercent[X_AXIS], 0, 100, dac_driver_commit);
       MENU_ITEM_EDIT_CALLBACK(int3, MSG_Y " " MSG_DAC_PERCENT, &driverPercent[Y_AXIS], 0, 100, dac_driver_commit);
       MENU_ITEM(submenu, MSG_RETRACT, lcd_control_retract_menu);
     #endif
     #if ENABLED(DAC_STEPPER_CURRENT)
-      MENU_ITEM(submenu, MSG_DRIVE_STRENGTH, lcd_dac_menu); 
+      MENU_ITEM(submenu, MSG_DRIVE_STRENGTH, lcd_dac_menu);
     #endif
 
     #if ENABLED(EEPROM_SETTINGS)