Masa

I wonder if there is any way to keep the menu bar and dock visible on the main display, but not on the 2nd display (in my case, a jit.window in a fullscreen mode for projection).

how-to-keep-the-menu-bar-visible-on-the-main-display-but-not-on-the-2nd-display

Not sure if this is what you mean, but in System Preferences, Mission Control, you can disable the 'Displays have separate Spaces'.

Thank you for your advice JVKR. Unfortunately it did not work. I am trying to see the menu bar on the 1st display, while keeping the menu bar hidden on the 2nd display.

How to keep the menu bar visible on the main display, but not on the 2nd display