Appending to a service conf file

I need to try and make a change to the gnome-session-restart-dbus.service configuration. The file resides in a few locations:

/nix/store/zdnsa0lajm2idzwgcfyfi04jvyf24lqp-user-units/gnome-session-restart-dbus.service
/nix/store/30q3li59cba9j24ibfgmmc2p07p1npkq-gnome-session-40.1.1/share/systemd/user/gnome-session-restart-dbus.service

I can’t find a relevant nixos-option to make a change to this file, what’s an appropriate way to do it?

Hello @jrobinson-uk,
it seems to be an user unit and if it is installed my bet is that your system has a systemd.user.services.gnome-session-restart-dbus option. You can add your config there.