Does anybody know if I can create multi-level lists? I haven't found a way to do this yet - maybe it isn't yet supported.

I.e. I'd like a list called Computing, that contains another one called Languages, that contains another one called Ruby, that contains all my Ruby bookmarks.

This is how I organize my local bookmarks in browsers. Diigo is very cool, but until I can get to my Ruby bookmarks from the toolbar in three clicks, it ain't gonna be as useful to me as my local bookmarks.