For reference sake, the structure part for that (in the form I current use, which might change at will) looks like this:
[{1,[2]}]
But that only works if it really is a recursive structure, i.e. if every id refers to a record in the exact same schema. For my data that holds true, but in your example you have separate schemas for files and folders. I guess though that it’s merely a consequence of the oversimplification of the example you’ve constructed. I too have very many schemas involved in the node, and I need and load them all for the components to turn into HTML. I count all of that as one node with one id of the recursive schema which eventually gets to a list of records (with ids) of the same schema again. Those would be the next (child) ids that goes into the tree structure. Nothing else.