I became totally dependent on Panorama/Tab Groups functionality, so I really welcome the effort to bring it back in webextensions! A major milestone has been reached as tab hiding now works without any hacks in Firefox 59 Beta 3! No need to fiddle with a Nightly build anymore, Beta is almost release quality! And I can finally retire the ESR version that I kept for compatibility with old Tab Groups...

The only tweak I'd do now is to enable switching to another group/container by simply clicking on it, without the need to "unwrap" it and pick a particular tab (just like the old Tab Groups - left part of the list item goes to group, right part with number of tabs unwraps it).

Thanks for this invaluable tool!

Edit: Just realized that Fx59b3 is not officially out yet, I tried a candidate build. But it will be released soon.
Edit2: Thanks for promptly implementing my suggestion, upgrading my rating from 4 to 5 stars!