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)

When selecting tabs, it opens them. It never did this before, how to select without opening the tab?

Thank you very much for developing and supporting this add-on!
I switched from chome to firefox some month ago and selecting multiple tabs and dragging them to different browser windows was a feature I realy missed when I was working with firefox.
Now you made the plugin perfect by adding this drag and drop support! Thank you so much!