nixos-config/modules/applications.nix

{ config, lib, ... }:
with config.deviceSpecific;
{
  options = with lib;
    with types; {
      defaultApplications = mkOption {
        type = attrsOf (submodule ({ ... }: {
          options = {
            cmd = mkOption { type = path; };
            desktop = mkOption { type = str; };
          };
        }));
        description = "Preferred applications";
      };

      startupApplications = mkOption {
        type = listOf str;
        description = "Applications to run on startup";
      };
    };
  config = {
    defaultApplications = {};
  };
}