I think the problem is here: PKGBUILD · master · Packages / extra / heroic-games-launcher · GitLab In line 56 the value of exec is missing the %u argument.
If someone has the same problem (most probably with apps like cartridges not working with heroic) u can go to /usr/share/applications and edit com.heroicgameslauncher.hgl.desktop
the exec line should look like this:
Exec=heroic %u