Stacking is great in some situations. It's a nice tool to have and I do use it. But nested notebooks (just two levels even) and !!! manual sort !!! would bring a much more productive and efficient workflow to EN for some of its users.
+ 1 billion for manual sort My current solution... Manual sort of Notebooks and notes and nesting Notebooks (even just a couple of levels) would make EN the go to for all my personal and professional projects rather than just some of them.