You should try Tab Manager Plus, it's the best Tab Manager IF you change the default settings ! (video demonstration)
Tab Manager Plus
Set to "Open in own tab by default"
Set to "Dark mode"
Set to "Vertical view" -- very important
You can live search your tab titles to select them
You can open all selected tabs in their own window
You can close selected tabs
You can "discard" tab contents (different from close, the tab is there but content is gone)
You can highlight/select duplicate tabs
You can hide not selected tabs
You can pin selected tabs (unfortunately, they still only appear on the one window they are pinned to, they just get pinned to the left of the tab bar)
You can drag and drop selected tabs to another window of your choice, both the representation of that window in the TMP tab, but also into the other firefox window itself. That means, drag and drop from here, is the same as pulling out a tab out of a normal firefox window !
Cannot search text inside of tabs, especially not sleeping tabs
Sometimes I press the TMP button and I just get a bluegreen screen, doesn't work until I close many windows and tabs
I would prefer real dark mode with my preferred colours
I would like to easily drop&close tabs into bookmark folders reliably !
So I have made an add on called Tab Kraken which is less advanced (and definitely less pretty) than Tab Manager Plus. It doesn't have all the same features but it would be wrong of me not to share here.
To be clear I'm not claiming this is as good but the layout might suit some people better.
Thanks for the suggestion, I hope you keep working on it.
While Tab Manager Plus is great, it is also abandonned.
Do not hesitate to steal all its good ideas !
Web power users need more than Tab Manager Plus has to offer