From looking into this s a few days ago it looked like things were packaged in the unstable channel so you can install them. But from what I read there is no way to configured it via nix configs so you would manually have to write them for now.
There is also this flake which should give some configuration for it but it mentions it might not be dully working yet and I have not yet actually tried it.
I don’t expect things to change much in this regard though until they start releasing some more stable versions of cosmic which is still in a prealpha state.
From looking into this s a few days ago it looked like things were packaged in the unstable channel so you can install them. But from what I read there is no way to configured it via nix configs so you would manually have to write them for now.
https://nixos.wiki/wiki/COSMIC
There is also this flake which should give some configuration for it but it mentions it might not be dully working yet and I have not yet actually tried it.
I don’t expect things to change much in this regard though until they start releasing some more stable versions of cosmic which is still in a prealpha state.