(I have not tested this in the regular 23w13a snapshot)

In the 23w13a_or_b snapshot, whenever you click on the buttons under the "More" tab in singleplayer, the buttons remain highlighted until another button is clicked. The same applies to the "experimental" button under the "Game" tab in singleplayer.

The highlighted buttons returned to normal when I went to the main menu and then returned to the single-player menu.

Main Menu - The one where you select single-player or multiplayer, not the in-game one.