Would it be possible to add the Radio off and the Screen off buttons at the bottom of the Main Menu Screen, between the Phone and the Settings options? I find sometimes at night the screen seems to bright and would like to turn it off without going into setting menu.

Certainly sounds doable. I'm not sure how easy it would be to add this to that menu though. I know people customize the navi screen all the time, and that would certainly be easy.

Another thing you might do is hold down the map button, which brings up screen brightness immediately.. then you could turn that all the way down to lower the brightness.

Or you may even find a way to program that holding in the map button automatically shuts off the screen.

While that may very well be possible for someone with the correct toolset and the required know how (like leetcoder), it's actually not that easy.

Although most of the different components (navigation, menus, audio screens, etc.) look similar, they're actually totally different software packages written in different languages.

The majority of the modifications in this forum all deal with the navigation software on the system. Something like turning off the audio source or screen backlight is a higher level function that will take quite a bit more work to integrate with the rest of the system.