@fadingrose We were talking on the Commander X16 discord and it seems that there is consensus to let the emulator handle ALT+F4.
On normal use, that key combination will never reach the emulator, but when running under emulation station, that combination will reach the emulator and I have created a new branch that handles that.

I am not sure how familiar you are with git, but you just do

git clone https://github.com/JimmyDansbo/x16-emulator.git git checkout alt_f4