This is indispensable, I use it to manage my many tabs. But there has been a few issues since Firefox switched to WebExtnsion (not really the dev's fault)

In the latest version tabs don't stay in the same place after restart, I have grouped tabs for similar topics but they are all over the places after restart.

Also, the first tab loaded after restart always moves to the first position (from the left) no matter where it is.

I checked the option open tab next to current if that matters.

Also search never works since FF57. have to use filter for all tabs.

Thanks for the great work. I rate this as 4 star despite the issues since these are not the dev's fault and I am sure he will work on them.