If you switch to desktop mode while zoomed out (like ~90%), the toggle to switch back just straight up disappears. You basically get stuck in desktop mode unless you mess with zoom again.
Setting zoom back to 100% (or sometimes even higher like 130%) makes the toggle show up again.
Seems like it’s tied to screen size / breakpoints, so zooming messes with it.
Not a huge issue for most people, but kinda annoying if you use the toggle and can’t switch back.