How to apply gsettings in NixOS?

Hi,
I’m also struggling to apply settings to gnome-Apps.
Based on this posting, I created this:

  programs.dconf.profiles.user = {
    databases = [{
      lockAll = true;
      settings = {
        "org/maliit/keyboard/maliit" = {
          enabled-languages = "['de']";
          theme = "BreezeDark";
        };
        "org/gnome/desktop/wm/preferences" = {
          button-layout = "";
        };
      };
    }];
  };

the button-layout configuration is working, but my Maliit-settings seem to be ignored.
Has anyone an idea, what I’m doing wrong?