I'm sorry but I have to say, I think that design decision for tab groups in vertical tabs is bad and flawed, and I say this as someone that loves tab groups. It's just unnecessary to have that margin/padding for tab groups, the colored line is more than sufficient AND you would be able to have those tabs follow Fitts' law too. Look at how tab groups work in horizontal tabs: there's no margin and I cannot think of an issue with that UI/UX.
No disrespect but I think the Edge team is not appreciating how annoying this Fitts' law vertical tabs issue is. It's really harming the user experience for vertical tabs. I respect the Edge team and I'm not one of those people that try to tell people how to do their job but this Fitts law vertical tab thing is so obvious. Could yous please reconsider? Maybe do some user testing and ask the Insider community what they think about this? Or try this experiment and see how users react: for horizontal tabs mode, move the tabs down a little bit, which would ruin the Fitts' law effect when the window is maximized. I guarantee that you would instantly get a flood of complaints! And that's because without it, targeting tabs is just slower and requires more effort/care. It would be a huge usability downgrade, and that's how Edge's vertical tabs UI has been all along :(
