If you're a bit more conservative with your screen real estate, I'd recommend the Tab Kit plugin instead: https://addons.mozilla.org/en-US/firefox/addon/5447 h

If you're a bit more conservative with your screen real estate, I'd recommend the Tab Kit plugin instead: https://addons.mozilla.org/en-US/firefox/addon/5447 https://addons.mozilla.org/en-US/firefox/addon/5447 It includes the vertical tree-style sorting, but I prefer the horizontal mode with several rows of tabs visible -- it lets you see more at a glance. It also color-codes each group of tabs uniquely, and lets you collapse groups. It's a handy way to open a bunch of research on one topic, then set it aside for later.