I know that there is a way to disable global menu. I don't quite want this as I quite like (at least one thing about) global menu. I would like to know if there is a way of disabling global menu for non-maximised windows.

Thus I ask: is this possible and if so, how is it done?

To me, the menu bar/global menu should be visually a part of the window since it is a part of the program and the window is meant to encapsulate the program.

Global menu is only visually a part of a window when the window is maximised and merged with the top bar. I don't like bits of my windows floating all around the screen. You wouldn't drive a car when the driver's seat is on the roof of your house.