Thank you for your replies to my topics. I replaced what I had done with your command instead, and it now works properly.

Even though I've set Mesen to close with the Esc key, it stays in the background when mGalaxy is open, and then when I try to launch another game, it doesn't show up. Can someone please create a script to fix this? I replaced the emulators name in the Snes9x script and compiled it with Autoit, but ...

It took me a while to find out where I had to add "/fullscreen"  manually (the UserSystems.xml file) to use Mesen with mGalaxy.

It is maybe the most actively developed specialized NES/Famicom emulator right now. Please add automatic support for it to your default script.