I forgot to continue writting:
In this later case of misbehaving .desktop file, it's often needed to *copy* the .desktop file that is made available in the Guix profile of the current user, and modify it for your needes. When done, perhaps you can send a git/unified patch to Guix project so that they apply your modifications (and you also get the chance to put your copyright holder line in the relevant files, so you can participate in some decision making and license compliance enforcement in the future, if you so desire).
