Outside of the Symbol (make sure you exit it), create a new Custom Behavior (at the bottom of the Scene Inspector).
Inside of your persistent element (I think you mean persistent symbol?) you can then create a mouse click > Trigger custom behavior action. In the dropdown, select your custom behavior.
The Scene where you originally created your custom behavior needs to be shown. You could also of course create custom behaviors across persistent symbols if you want the action to work on any scene where those two objects are present.