I'd love the option to have Firefox use the space that is now a black bar (where the notch is and the menu-bar normally is on 2021+ macbooks) for the tab-bar. I don't use many tabs and by moving up the interface into that unused space it clears some vertical space for actual content instead of having a useless black bar on a screen I paid for 🥲
The tab-bar could extend the full width of the screen and jump around the notch (like the menu bar in full screen does) or be placed on the right side of the notch while the left is used for the menu bar.
Chances are Apple prohibits this behavior because, well, Apple. If so, ignore this request!