Manage dconf via keyfiles

Managing configurations via dconf in NixOS is not very pleasant and unsatisfactory. I would like to test a dconf configuration with plain text files.

However, this requires the entry service-db:keyfile/user in the profile /etc/dconf/profile/ which is currently gdm with the following content:

       File: /etc/dconf/profile/gdm
   1   user-db:user
   2   file-db:/nix/store/ws1vi3yi1p5d5lmkm7zh0kc8mh77rayz-gdm-dconf-db
   3   file-db:/nix/store/ddkv22340gb7v5zazzbngljc6dmxvjkv-gdm-40.1/share/gdm/greeter-dconf-defaults

Can I somehow inject the line service-db:keyfile/user between 1 and 2?

Maybe related to nixos/dconf: Allow creating custom databases · Issue #54150 · NixOS/nixpkgs · GitHub