What you have to do to be a developer of Android Auto
Install an alternative Launcher (Car-Launcher or Nova-Launcher or some other)
Running alternative launchers you can open Android Auto
Open AA (AndroidAuto) settings by tapping on the three lines in upper left corner (menu)
Scroll down to Version
Tap about 10 times on Version and a message will appear. Answer ok.
Now tap on the three dots (upper right corner) and tap on Develpoer settings
Select developer in Application mode.
Now you are able to alter some settings to your liking.
Disclaimer: I'm not responsible for any faults you make using developers power. I'm only resposible for the information that you can do more than you suggested.
Bye for now Fred
Still can't get rid of huge media notifications 😭