Hi, no idea. Mozilla only ok's the Developers Extension to work on Firefox and provides them with a web page to distribute their Extension. Below has Home page, support page and email info.

• https://addons.mozilla.org/en-GB/firefox/addon/sync-tab-groups/

I will say if it is lost, it probably will stay lost.

Please let us know if this solved your issue or if need further assistance.

But isn't there somewhere where it dumps all the data?

I assume that this extension uses storage to store this data if I check its permissions.

So there could be a problem with local storage. I think that there will be Firefox update to address issues with local storage, but I don't know when this version is ready to be released. You can wait to see if this update fixes the problem if you can't fix it otherwise. I assume that you didn't use the refresh feature in Firefox to create a new profile.

I don't know what refresh feature and profiles refer to. Maybe all this happened when Firefox was updated recently. Surely there's a folder location where open tabs data is stored.