Earlier quoted context omitted.
It would except the user interface will be stripped so bare you can't actually have more than a dozen or so pages open at once! I know there are many people in the same position as me. They open a lot of tabs. When Google killed off vertical side tabs (which were only ever a hidden option you had to enable manually anyway), they went back to Firefox. And now Firefox is taking the vertical side tabs out in the street…
https://testpilot.firefox.com/experiments/tab-center/
1. No that is not a Replacement for TreeStyle Tabs, far from it
2. It uses XUL as well and will be killed in 57 unless new API;s are made
this link is not the solution to the Extensions problem we are complaining about