Interesting, thank you! So that means programs are sometimes patched to look for configs in nonstandard locations generated by Nix during installation time. But then if I wish to change any of those configs (maybe to change one of the defaults)... I have to copy them, make my modifications, generate my own package for them, and install them to wire them in as substitutes for the existing packages. Then when the upstream package changes the config file, I have to generate a new package with all the conflicts manually resolved, right? It seems a bit of an arduous process, though I do see the appeal.