Counters and sub menus

Hi all. New to module creation. I am starting with the Elemental Clash module. I am trying to add another type of counter to the game. Currently you right click on a card, and there is a Counter menu with Add and Remove counter sub menu. I would like to add another menu to add/remove a different type of counter.

After fooling around for a couple hours, I was unable to figure it out. I could get the new menu to show up no a right click, but it didnt have the sub menus. Is there a good tutorial out there for creating submenus and counter add/removes?