Installing a plasmoid from user profile [solved: refresh ksycoca after deleting its cache]

I’m trying to use kup (GitHub - spersson/Kup: A backup scheduler for KDE's Plasma desktop) for managing my backups from kde/plasma. I have been able to build it and install it in my user profile, by adding the following file ~/.config/nixpkgs/overlays/kup.nix:

super: self:

  kup =
    let pname = "kup";
        version = "0.7.3";

    super.stdenv.mkDerivation {

        inherit pname version;
        src = super.fetchFromGithub {…}
        buildInputs = with super.pkgs;
        [ cmake ] ++
        (with qt5; [ qtbase ]) ++
        (with kdeFrameworks;
              [ extra-cmake-modules kdbusaddons kcoreaddons
                ki18n kio solid kidletime knotifications
                kiconthemes kconfig kinit kjobwidgets plasma-framework

Then, I’m supposed to configure kup from the configuration center in plasma (or through kcmshell5), but it does not appear there, nor in kcmshell5 --list). This is expected, since plasma does not know about my user profile. Thus, two questions:

  • What is the list of places where plasma5 looks for kcm stuff on nixos?
  • Is there / should there be a way to make plasma look into my user profile for kcm stuff?

Solved: to make kup known to the plasma desktop, it’s enough to delete all ~/.cache/ksycoca5_* files and run kbuildsycoca5. Then a “backup” section appears in plasma’s configuration tool.