Detach or fully flatten tab? (single tab or a tab and its children)

[WildSnail913]

Wondering if theres a way to do this other than via drag and drop. I tried binding an Outdent hotkey but it doesnt seem to work when a tree has same tab-depth siblings.

I dont really understand the default Flatten context menu option either, I only ever use it when I want to flatten an entire tree by selecting all its children.

P.S.
I cant tell if this option doesnt work or if I'm expecting it to do something different than it does.

With this option Off I would expect any new tabs opened from a tab 2 levels deep, to also only be 2 levels deep. Leaving tree management up to drag and drop. But it doesnt seem to do that?