Show sub-items as Badges. (I know, I know. We don't need no stinkin' badges har har har)
Show sub-items as "category sets". In-game, you'd see these as a vertical list of child presentation nodes - armor sets for example - and the icons of items within those sets displayed horizontally.
Use the "default" view for the presentation nodes.
A hint for what screen should be shown when this presentation node is clicked into. How you use this is your UI is up to you.