Sidebery without using trees because they waste valuable tab name space. Having more name space is a key advantage to vertical tabs. I use separate windows for high level categories and use the titler extension to name the windows. Sidebery doesn’t recognize the titles when you want to move a tab to a new window though. That’s one of a few pieces of kruft in my setup.
Mozilla sucks, but it is because all of this should be baked in, not because of pocket or whatever political thing that HN regularly brings up.
I have tried the vertical tab implementation in several other browsers and they are all inferior. Safari’s is hilariously bad.