P3Dv4 was installed by me a couple of hours ago.
The very first scenery installed was my lovely Jutland North, and it appears to work perfectly in daytime flight.
Please note that I have not checked night scenery yet. I've not spent much time seeing if all of the scenery elements are present at each airport. I wouldn't be able to tell if something was missing - there are more eagle-eyed people out there than me to do this, but so far so good.
I created a new folder in my P3Dv4 directory called \ADDON Scenery.
Next I cut and pasted the Vidan Design folder from P3Dv3 into this new ADDON Scenery folder.
Then I started P3Dv4 to enter the P3Dv4 Scenery Library Editor and manually entered as a new entry for each of my Vidan Denmark sceneries (I have them all) - Jutland North, then all of the airports in turn, pointing the editor to the relevant folder for each scenery.
So far, I have not visited all the airports yet - so much to see and check with a new sim to play with - but Jutland North, and the 6 airports I checked so far all seem to appear correctly.
There were a lot of stutters that dismayed me, until in settings I clicked on Vsync and set a max framerate of 30. Now it is nice and smooth on my 65" Samsung 8000 4K TV that I use as a computer monitor. Flight sims are a joy to behold when experienced like this.
I will uninstall P3Dv3 completely as I get my new scenery and aircraft updated for P3Dv4, and I have only one copy of the Vidan scenery on my computer, in just one sim (P3Dv4, now).
John, please let me, and the Board, know if this violates any User Agreements, and I'll be happy to correct matters.
Just thought that people moving to P3Dv4 would like to know that so far it seems to work well on the new sim.