I think rttr can be removed as a dependency.

Also, It is also possible to switch qt-build-system. In this case, the manual XDG_DATA_DIRS, QT_PLUGIN_PATH, and QML2_IMPORT_PATH wrappers can be removed. The resulting wrapper is slightly different but I think equivalent.
I attached a patch I made last week. If you think it's good you can use that or make it in to your own patch.

Also, there is another kdenlive bug report here https://issues.guix.gnu.org/38450 . I think this bug actually isn't
present any more. To the reviewer of this kdenlive update, if you have the time, maybe also check if that bug occurs, and if not close it. Thanks.