The list of systems and emulators is not made editable because it is replaced at each update of mGalaxy by the new version and overwrites the previous one. The goal is that each user, whatever his technical knowledge, can benefit from the latest advances with each new version.
It doesn't release a system or an emulator every day and when it does, the user who wants to integrate it to the official list is asked either to make the request or to do the "work" beforehand and send the result on the forum so that it can be integrated and that all users can benefit from this addition!
An option to restore the default setting for backup would be awesome
The original files are present in a folder called 'Install Files'