Hi Bruce, did you make a backup using a feature of Simple Tab Groups, or do you mean you have a backup of your Firefox profile folder and the Simple Tab Groups data should be in there somewhere?

I've read this a few time and I think i have the same question. I have setup groups of tabs. When i save and close the group I can't find where to reload/restore the groups. Ultimately I'd like to have the groups pinned. I recently moved away from Arc and this (for me) was its best feature.

Are you also using the Simple Tab Groups extension? STG has a sidebar that lets you switch your view between different groups of tabs. Does the set of closed tabs appear there? I'm sure it also has more advanced features to view simultaneously in different windows, etc., but I haven't tested it for a couple of years so I can't remember the details.