I've been looking for something like this. It was just two weeks ago I had Claude modify Wezterm to add tree-style vertical reorderable tabs. It works OK but your solution is nicer.

So I've been using cmux for a few hours this morning, and I like it. One thing I'd like to disable is the reordering of tab groups. Currently it shows the most recent notifications on top. This also makes the keyboard shortcut for a given conversation change all the time, which is a cognitive burden for me.