Hi, this is not an issue/problem since the vertical tabs support for full screen mode simply hasn't been implemented yet.
comment from an Edge developer: "vertical tabs aren't enabled on any platform in full-screen yet since we're still determining, among other things, the interaction that would make the most sense. "
Vertical tabs in fullscreen mode were working a few months ago, however they were a bit buggy. In a frustrating update, the feature was entirely disabled in fullscreen mode again and is still fully disabled. I believe the ability to use vertical tabs in full-screen mod was probably a bug before with how they disabled it on Mac, letting you re-enable vertical tabs in full-screen mode when you weren't supposed to be able to in the right-click context menu.
It technically isn't a bug now, but it is something that would be nice to have. Having to keep Edge in a shared/normal desktop instead of being able to fullscreen the application is a frustrating limitation in MacOS, where full-screening an application is the only way to give it a dedicated virtual desktop (a workflow I think is a little easier in Windows).
I still don't understand why this issue hasn't been fixed up until now. It clearly is a big usability issue on macOS. Why doesn't Microsoft just disable completely this feature on macOS if they don't plan to do it decently?
More than two years later and still no vertical tabs in full-screen mode on macOS... This is definitely a problem for many users. Perhaps there are technical hurdles that can't be overcome? Vertical tabs is one of the main features that keep me loyal to Microsoft Edge. If I discover another browser that can achieve this, it might be enough to make me switch.
