Do new tab groups work with the new native vertical tabs?
Just tested, and yes.
Is there something you have to enable? I have vertical tabs enabled and nothing happens when I drag one tab over another, no visual cue, nothing.
It takes a second or two for the grouping option to appear.
I see on the tab groups site:
"This feature is experimental and is being introduced to the Firefox user base through a progressive rollout. It may not yet be available to all users. "