Update Brave, yesterday there was an update for this, to revert the hide tabs in Fullscreen, which is something I have seen browsers doing all the time, and that was a problem because Full screen doesn’t show horizontal tabs but was showing vertical tabs.
So, I don’t know how full screen works in MacOS and I don’t care to understand it, but today on Nightly, Brave already implemented a ‘hover to show tabs in full screen’, that means, Stable eventually will get it, where you can go full screen but still get tabs if needed when you hover the left side of the screen.