Install

nix-plist-manager comes as two modules with the same options:

home-manager manages your settings: appearance, the Dock, the trackpad, keyboard shortcuts, Finder, anything System Settings keeps per user.
nix-darwin manages the machine’s settings, as root: the firewall, sharing, power, date and time, software updates, the login window.

Each settings page marks every option with the module it belongs to. Most people want both.

Add the flake

{
  inputs.nix-plist-manager.url = "github:sushydev/nix-plist-manager";
}

Import the modules

darwinConfigurations.my-mac = nix-darwin.lib.darwinSystem {
  modules = [
    nix-plist-manager.darwinModules.default
    home-manager.darwinModules.home-manager
    {
      home-manager.sharedModules = [ nix-plist-manager.homeManagerModules.default ];
    }
    ./configuration.nix
  ];
};

darwinConfigurations.my-mac = nix-darwin.lib.darwinSystem {
  modules = [
    nix-plist-manager.darwinModules.default
    ./configuration.nix
  ];
};

homeConfigurations.me = home-manager.lib.homeManagerConfiguration {
  modules = [
    nix-plist-manager.homeManagerModules.default
    ./home.nix
  ];
};

Set something

In your home-manager configuration:

programs.nix-plist-manager = {
  enable = true;
  options.applications.systemSettings = {
    appearance.appearance = "Dark";
    desktopAndDock.dock.size = 48;
  };
};

And system-wide, in nix-darwin:

programs.nix-plist-manager = {
  enable = true;
  options.applications.systemSettings = {
    network.firewall.firewall = true;
    general.softwareUpdate.automaticallyInstallMacOSUpdates = true;
  };
};

Then rebuild (darwin-rebuild switch, or home-manager switch).

Don’t want to write it all by hand? Start from your Mac.