I thought copying the .desktop inside the AppDir root would copy it to /usr/share/applications but apparently it's not, though not picking up the reason why there should be two copies or a link to the root one: https://docs.appimage.org/reference/appdir.html#id3
Contains desktop files for applications in bin. Normally, there’s just one desktop file in this directory, which is symlinked in the root directory.
I thought copying the .desktop inside the AppDir root would copy it to /usr/share/applications but apparently it's not, though not picking up the reason why there should be two copies or a link to the root one: https://docs.appimage.org/reference/appdir.html#id3