Don't push effects that can't be undone onto the Undo Stack

src/Menus.h

@@ -369,6 +369,8 @@ public:
    static const int kConfigured = 0x01;
    // Flag used to disable saving the state after processing.
    static const int kSkipState  = 0x02;
+   // Flag used to disable "Repeat Last Effect"
+   static const int kDontRepeatLast = 0x04;
 };
 
 bool OnEffect(const PluginID & ID, int flags = OnEffectFlags::kNone);