This add-on is not ready for Quantum. When i Installed it crashed not only my firefox but also whole machine.
In Proccess Explorer Firefox had take in seconds whole 8 GB memory of my Computer without finally creates the onetab bar with me 230+ allready opened tabs. I gave it more than 20 minutes to work for build the bar but fatally didn;t make it.

I had to open task manager to kill the proccess tree of firefox for about 3 times, cause even after the first tries to kills the firefox proccess when i repopened it crashed again. Finally among 3th restart of firefox after a machine restrat it gave me some time to prior uninstall the addon and release the browser from this memory killer. Thanx Luck...i had install the session manager, cause after all these problems finally it had lost all my tabs from tabbar. I restored a previous session of past day and saved my tabs.

I hope they resolve the problem cause, it makes BIG problem to users.

I have only Tab Session Manager active and new tab tool not active