Unfortunately, this extension, too will soon die when Firefox no longer supports legacy addons.
I think there is a new Firefox experiment that behaves somewhat like this: https://testpilot.firefox.com/experiments/containers
I think there is a new Firefox experiment that behaves somewhat like this: https://testpilot.firefox.com/experiments/containers
Container tabs is totally different, that's about basically having multiple profiles in one window. E.g you can have the work container logged into your work email and work stuff, and your personal container logged in to your personal email and personal stuff, and they don't know about each other. Like incognito, but persistent and within the same window.
The 'simplified' in its name makes me doubtful it has any of the advanced features I need.
These "redone" addons that work post 57 start out pretty bare-minimum but they rapidly gain features.
Tab Groups has a shot. I took on this project after it was
decided to remove the built-in Tab Groups from Firefox, as
I thought it could be a good and fun learning experience;
it hasn't been, if anything it's been stressful and
time-consuming. I don't really use groups outside of my
development profile, with my browsing habits I only find
them useful to a point, they're helpful for my
development/coding workflow, but I've used them maybe twice
in my main profile during normal browsing.
Its core functionality and basic workflow probably can be
made into a WebExtension, but only after an almost complete
rewrite of the code (with some major work done on Firefox's
side as well!), and still stripped down of at least some of
its features. Many of the new groups features I've wanted
to add since the beginning are impossible though, for the
same reason as I mentioned above: they either don't fit the
scope of what can be allowed through WebExtensions or their
implementation would be far too complex to do on my own.