I’m dismayed to see that tab-groups is scheduled to be removed from Firefox (announcement here). It’s one of my favorite Firefox features and a big reason I don’t use Chrome, the other being support for privacy in the Mozilla Manifesto. I always have a pile of tab-groups open:
The good news is that in the announcement, Mozilla includes a link to the new tab-groups add-on, which will work pretty much like the existing functionality. Install it. Live it. Get your tab-groups on!