After entering macOS fullscreen, you cannot reveal the menu bar or dock by navigating to the edge of the screen (prior to snapshot 6, this only happened upon clicking "Fullscreen" in the Video Settings menu)

Starting in 26.3 snapshot 4, clicking the Fullscreen button in Minecraft on macOS toggles macOS fullscreen mode for the game. I’ve been eagerly awaiting this day, since having two fullscreen modes was always confusing, and I’m quite pleased by how well the new behavior works. There’s just one small issue, and quite an interesting one- if you enter fullscreen by clicking the Fullscreen button in video settings, you cannot then reveal the top of the window or the menu bar by navigating to the top of the screen, nor can you reveal the dock by navigating to the bottom of the screen (haven’t tested with the sides). Switching to another app and back does not fix the issue, instead you must exit fullscreen (by any means) and then re-enter it using a keyboard shortcut or the green traffic light button.

I honestly think it’s kind of cool that there’s a way to avoid revealing these system elements, since I’ve revealed them by accident on many occasions. At the same time, there have also been many occasions when I’m glad I was able to reveal them without switching to another app first, so if you’re going to preserve this behavior in any form, make sure players know they’re opting into it. Fixing this issue without providing an alternative means of doing this is still better than leaving things as they are.

Edit: while in this state, if you manage to reveal the title bar, it will not go away until you exit and re-enter full-screen. This may be a macOS issue, but regardless it would be great not to have to deal with it anymore.

Edit 2: As of Snapshot 6, you cannot reveal the menu bar or dock regardless of the method used to enter fullscreen mode. If you enter and exit Mission Control, you can do so again, but switching to Minecraft by any other means does not work.