Switched to Sidebery from Tree Tabs, definitely better, especially regarding performance. I have 300+ tabs, since I switched to Sidebery, Firefox's RAM usage is half.
https://support.mozilla.org/en-US/questions/1396277
Sidebery solved that successfully.

The only option I miss is unloading tabs/pages upon a predefined time interval. I'd set it to 1 week.

Tab Management 5.0. Best Tab Organizer. Must have! I have tried various and this is best in stability and functionality.

I was a user of TST, but it's full of unfixed bugs and a ressource hog. SireBery solves ALL the issues I had with TST ! Amazing !

Сойдёт но немного неуклюжее.
Имеются баги!

Мне нравится

Doesn't work across multiple windows, which makes the entire extension useless to me. (every window acts as a completely separate instance with separate tab groups)

Someone recommended this as a replacement for Simple Tab Groups, which it definitely isn't because of this.

the best addon I have ever had. I can't imagine a web browser without this