This new web extension is really disappointing and lacks the features of the original add-on.
I can't have both bookmarks tab open AND tree style tab open at the same time, which is a big letdown for me.
I can't close "all child tabs" at once anymore by clicking on the right click menu.
Can't close multiple tabs at once with a simple middle click on it as it always asks if I want to close multiple tabs before, which previously didn't for middle button.
When I close a tab, it tries to get the focus to the one under it (hence loading it), instead of the parent tab, and only half loads them (so that they remain buggy forever, until reload)
Also it doesn't work well with SNAP Links Plus, which, for some reason, creates useless temporary tabs with some weird indentation.
A lot of options disappeared from the add-on as well which makes it look like a watered-down rip-off of what it used to be.

EDIT :
The behavior of this add-on changed for the worst in the latest patch.
It now auto expands ALL the children and ALL their descendants upon tab selection (and not just those that were expanded before, like in previous versions)

There's no way to revert to the previous behavior and it's really annoying to have those huge FULLY expanded threes I didn't ask for.