Always enable leveling after G28

Marlin/Configuration.h

@@ -1284,10 +1284,12 @@
 //#define MESH_BED_LEVELING
 
 /**
- * Normally G28 leaves leveling disabled on completion. Enable
+ * Normally G28 leaves leveling disabled on completion. Enable one of
- * this option to have G28 restore the prior leveling state.
+ * these options to restore the prior leveling state or to always enable
+ * leveling immediately after G28.
  */
 //#define RESTORE_LEVELING_AFTER_G28
+//#define ENABLE_LEVELING_AFTER_G28
 
 /**
  * Auto-leveling needs preheating

Marlin/src/gcode/calibrate/G28.cpp

@@ -241,7 +241,7 @@ void GcodeSuite::G28() {
 
   // Disable the leveling matrix before homing
   #if HAS_LEVELING
-    TERN_(RESTORE_LEVELING_AFTER_G28, const bool leveling_was_active = planner.leveling_active);
+    const bool leveling_restore_state = ENABLED(ENABLE_LEVELING_AFTER_G28) || TERN0(RESTORE_LEVELING_AFTER_G28, planner.leveling_active);
     TERN_(PROBE_MANUALLY, g29_in_progress = false);  // Cancel the active G29 session
     set_bed_leveling_enabled(false);
   #endif

Marlin/src/inc/SanityCheck.h

@@ -1445,7 +1445,7 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
     #error "AUTO_BED_LEVELING_UBL requires EEPROM_SETTINGS."
   #elif !WITHIN(GRID_MAX_POINTS_X, 3, 15) || !WITHIN(GRID_MAX_POINTS_Y, 3, 15)
     #error "GRID_MAX_POINTS_[XY] must be a whole number between 3 and 15."
-  #elif !defined(RESTORE_LEVELING_AFTER_G28)
+  #elif !defined(RESTORE_LEVELING_AFTER_G28) && !defined(ENABLE_LEVELING_AFTER_G28)
     #error "AUTO_BED_LEVELING_UBL used to enable RESTORE_LEVELING_AFTER_G28. To keep this behavior enable RESTORE_LEVELING_AFTER_G28. Otherwise define it as 'false'."
   #endif
 
@@ -1473,6 +1473,10 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
 
 #endif
 
+#if ALL(HAS_LEVELING, RESTORE_LEVELING_AFTER_G28, ENABLE_LEVELING_AFTER_G28)
+  #error "Only enable RESTORE_LEVELING_AFTER_G28 or ENABLE_LEVELING_AFTER_G28, but not both."
+#endif
+
 #if HAS_MESH && HAS_CLASSIC_JERK
   static_assert(DEFAULT_ZJERK > 0.1, "Low DEFAULT_ZJERK values are incompatible with mesh-based leveling.");
 #endif