How to create a selection menu in the inspector for classes and their methods?

I’m working on creating a more robust version of Unity’s event system to help facilitate development. While I already have it working in code, I’m trying to make a GUI to make things easier. I’ve been modeling the interface on what Unity already has for it’s EventTrigger system.

The issue I’m running into is that I’m not sure how to actually display classes and methods can be selected for when an event triggers. I know how to get them (using reflection), but I’m not sure how to store them, or more importantly, get the interface for them.

What I would like to have, would be something like the EventTrigger system.
78791-mq0if7f.png

Does anyone know how to get something like this?

If you are saying you don’t know how to create a same drop down menu. Try this,

selection = EditorGUILayout.Popup(selection, new string[]{"test1", "test2/submenu"});

78793-capture.png