I want my mail client to only have one tab, if i switch to another view, i can go back there by normally opening it again. Sure, some people will see this differently, so i think it would be good, to have an option to disable tabs.
I have the Supernova beta installed, and it has tabs - and it looks even worse, tbh. There's an option to hide tabs if you only have one, but the moment you select something from the sidebar (or from anywhere), it opens in a new tab and they appear again. Frankly, I expected a bit more from this redesign. Still no way to get rid of tabs.