It is restoring tabs, one by one, so when I had 5600 tabs, it was trying to restore (open) a 5600 tabs one by one.
Browser of course crashed, so I was not able to open my tabs.
It is not possible to make "auto groups" based on domain or regular expression.

Some people here are idiotic (the ones who store 10 years long tabs history and never backup it). This extension is holy grail. IT WORKS GOOD. AND HAS NO ADS. FOR YEARS. Princesses who can't backup your sh#t once in a month are meant to suffer in this society. Thx mr developer. The only suggestion is to add star icon for bookmark saving in the tabs list

I exported my tabs from the Brave extension to come to Firefox (well, Zen), and it didn't export the names of my groups. This isn't a big deal for me, except sometimes I've put videos in their with the tab name as the timestamp, so of course that's gone. It's not like,,, horribly confusing or whatever, just extremely limited I guess. And I also lose the add date of the info.

DANGER. The app slows down the system a lot. And if you use groups for tabs, it deletes them!

ОПАСНО. Приложение сильно тормозит систему. А если вы используете группы для вкладок, то она их удаляет!

This is by far one of my favorite add-ons - cleans up your browsing experience, saves on ram, and you still have access to get at old tabs. Awesome!

탭 복원을 하면 파폭의 탭그룹을 다 날려 버립니다.. 날아간 탭그룹은 복원할 방법도 없습니다. 와 내 탭들...

OneTab solves multiple problems, cleanly, for me. My feedback on further extensions got an immediate response (asking for more info). Go Team! My one issue with rearranging group members had a reasonable workaround (shrinking font size on OneTab page) until the full changes make it back out to us users.
You folks rock!