You can set the window Zoom Level to change all of the font sizes, including the menu, but afaik, there's no option for just the menu font size.
I guess if you want one size of menu font for VS Code, and a different size for everything else, then that’s a problem.
That seems like a pretty narrow corner case though.
You can set the window Zoom Level to change all of the font sizes, including the menu, but afaik, there's no option for just the menu font size.