I fixed my kden by adding
```nix
nixpkgs.config.packageOverrides = pkgs: {
  kdeApplications.kdenlive = pkgs.kdeApplications.kdenlive.overrideAttrs (oldAttrs: rec {
    postInstall = "wrapProgram $out/bin/kdenlive --prefix FREI0R_PATH : ${pkgs.frei0r}/lib/frei0r-1";
    nativeBuildInputs = oldAttrs.nativeBuildInputs or [] ++ [ pkgs.makeWrapper ];
  });
};
```
to my configuration.nix