Looks like this is the Bugzilla issue for providing the APIs to enable a Tab Groups port: https://bugzilla.mozilla.org/show_bug.cgi?id=1384515 ; "I've heard from several people that they're looking for an API that enables the usage of tabbrowser.showTab, tabbrowser.hideTab and/or tabbrowser.showOnlyTheseTabs. The primary use case I can point to right now is TabGroups (in fact I think this is blocking TabGroups from being ported to a WebExtension)."

The developer had put out a note saying that Tab Groups won't be suppressed by WebExtensions, and the work in order to do a partial port isn't worth their time.

"Something like it":

https://github.com/denschub/firefox-tabgroups https://github.com/kesselborn/conex