Create custom Triggerevent

Hi, I am currently trying to create physical Buttons, Levers etc. I want to add a way for them to call a funktion one they have been clicked. However I can not find a way to make a selector for a script in the Inspector tab (the same way I can create an option to select sounds/Strings ...). The best way to solve this would be to create a custom Tiggerevent, or somehow call an existing one, so I could use the build in Eventsystem. But I am not finding a way to do either of those.