Representing nested relations

Am I correctly interpreting that only top-level types within a hierarchical list are allowed to be recursive? Would it be possible to allow nested types to have recursive relations as well?

I’ve got two types, ideas and tasks (it’s sort of a simplified GIST approach). Ideas can have sub-ideas and sub-tasks. Tasks can also have their own sub-tasks. Currently I’ve got a list that shows nested ideas, but I can only make it show the first level of sub-tasks.