Duet Smart Effector support (#16641)

Marlin/Configuration.h

@@ -915,6 +915,13 @@
   #define Z_PROBE_RETRACT_X X_MAX_POS
 #endif
 
+// Duet Smart Effector (for delta printers) - https://bit.ly/2ul5U7J
+// When the pin is defined you can use M672 to set/reset the probe sensivity.
+//#define DUET_SMART_EFFECTOR
+#if ENABLED(DUET_SMART_EFFECTOR)
+  #define SMART_EFFECTOR_MOD_PIN  -1  // Connect a GPIO pin to the Smart Effector MOD pin
+#endif
+
 //
 // For Z_PROBE_ALLEN_KEY see the Delta example configurations.
 //