no new functions (for example export in different formats), visual/selection lag .

Nice. Basically required for Firefox use. (Firefox really needs to add this absolutely normal tab-handling functionality to the browser--Chrome's had it since the beginning.)

This may be the same as a previously existing extension called "Select and Do"? (It's been a while since I used Firefox, but this came up when I searched for that extension which I previously used for this purpose.)

I feel like I may have preferred that one, but I might be completely making this up and this may be the exact same extension with a different name. Who knows.

Does what it says it does, no bullshit

Does not move the whole selection of tabs to a new window, only up to 28 tabs. Seems to be limited in how many tabs it can handle. That's pretty poor for a "multiple tab handler".

EDIT:
Dont know why but today it started to work again, then I change from 1 star to 5 stars:). Hope it will not change tommorow:).

OLDER:
It was great addon. It was one of my corre addons in firefox. i am still on 56.0.2 (64 bit) firefox version. It worked great (stoped working in 2019), but now I dont have this function even i did not update firefox or this addon (it says it is still version 0.8.2017061501 (which is for a <57 firefox version). Also can not fin anywhere this version to reinstall it. It is very big loss for me, as i dont want to move to new versions and now I lost funcionality i use every day up to today :(. I would put 5 stars if it would work (or my problem would be solved)