I was actually thinking after my comment... what if you could hold down e.g. shift while resizing the browser to resize the window without resizing the viewport reported to the website? So you could make the window narrower, then scroll horizontally so the menu is off-screen.
I move a window past the screen partially when needed. But it doesn’t work well at two-display border. Another real option is to find a container div and pin its width via stylebot.
