Firefox tag groups / panorama has been removed from Firefox proper. Luckily, they’ve moved the official source to a separate project as an extension called Tab Groups. The extension seems to function the same and migrated my existing tab groups to without trouble.
I guess there is benefit to having less code in the core Firefox project to maintain, but this is one of those cool features that sort of set Firefox apart from other browser. There is a Chrome bug requesting a similar feature that has 356 stars and comments praising the feature. Development apparently stopped in Firefox years ago, so maybe this split could actually increase development, but there’s always the chance that it doesn’t get updated to work with a new Firefox version at some point and disappears. At least the code is on Github.
I think the features has issues, such as slowness, moving around of groups when resizing windows, and a bit clunky of a UI, but is the best option I’ve seen for dealing with large numbers of web pages and multiple topics, particularly in the short term. Right now, I have 383 tabs in 28 groups, plus a dozen or so tabs in two other windows. Some of them I probably haven’t looked at in years. I think for long-term storage, local or “cloud” bookmarks are the best way to go. I’d like to work on moving most of my tabs to my delicious account, or better yet, my own site, but even then, I will want tab groups for day-to-day organization.