OK, final short update and teaser
It's working on 5.4.0, and I implemented the possibility of independent sort for upper/lower panel. I am now at implementing the "sync" functionality (drag up/down to jump to the respective collection in the other panel).
I have to rush to catch a plane now... bye bye Europe, hello Africa! I'll be back in Mid January and will release a new version then. Merry Christmas and a happy new year to all!