What I do is "simply" have a bunch of separate windows open on multiple virtual desktops (and 3 physical monitors). It's effectively the same hierarchy, just wi

What I do is "simply" have a bunch of separate windows open on multiple virtual desktops (and 3 physical monitors). It's effectively the same hierarchy, just with only 2 levels (3 if you count virtual desktops) and I find I generally don't need more than that. Another thing that helps with tab-hoarding is a clever userCSS hack (from someone on Reddit) that puts my tabs into multiple rows so I can still read their titles, even if I have 20+ in one window. As for why it's not supported out-of-the-box, to put it a bit harshly, deep hierarchies scare "the normies". I find that more than 2-3 levels of trees are too much to remember for most people (hence the cluttered desktops and "bucket" folders).