This add-on is excellent. For my use case, web browsers are basically unusable without something like this. I've been on a a years long search for something like this that actually works well, with many disappointments along the way. There are several vertical tab organizing add-ons out there, but this has by far been the most stable one for me. I did have some instances of tab groups being lost, but the settings menu provides a suggestion for fixing this (under "Where to store tabs") which seems to have worked for me. It also looks good, functions well, and has lots of customizable options. On suggestion is to have the option to display the tab group names along side, or as an alternative to, the icons. Maybe I'm missing this option somewhere.