This add-on is crazy good. I used it every single day until Firefox introduced tab groups themselves, so I'd rather use the native solution than an extension, but if Firefox's tab groups seem to not work properly after all I know where I'll be coming back to.

Contrary to other reviews, I never had STG delete my tabs or anything like that. They have a backup option in case this happens, but since this isn't clearly communicated, people seem to be confused about the random STG backup folders appearing, or because they dont know about the backups they do not see a way to recover their tabs. If I had to remark on anything, it would be that this could be more clearly communicated.

Other than that, I highly recommend this extension. It's one of the best ones Firefox has to offer.