Custom Editor, drop down similar to shader menu

Is there a way to have a drop down menu like the shader menu where there are categories and subcategories? (Seen in the image below)

45053-capture.png

EDIT: Or, is there some way to indent in the popup menu?

Yes this is possible and it is called a Enum, i have used these before and tried doing some research on Sub Categories but it would take some time. (In my opinion you dont need Sub Categories because people wont see them in the gameā€¦) and here is a example script.

using UnityEngine;
using System.Collections;

public class ExampleEnum : MonoBehaviour {

	public enumtest test;
		
		public enum enumtest {
			Choice1,
			Choice2,
			Choice3,
			Choice4 // <<-- Dont add a comma on the last one!
		}
	}