I am trying to get this to work in P3Dv4 and hit a snag. The airport has no buildings. ADE will not compile it and I get an errors list so I can't add hangars etc with the Library Object Manager. Using the fault finder tool there are the common errors of missing links and nodes, etc but all my AI aircraft work fine and the scenery looked good back when I had FSX (see screenie).

I also tried to import the Key West Object Library.bgl to MCX but it says it's just an object placement bgl. I think then this means it calls for all the buildings in the MAIW Library Objects folder. But that is a whole lot of objects and I cannot tell which ones in particular are needed for MAIW KNQX and I need to convert to P3Dv4 in MCX.

Question: do the some or all of the scenery objects in the MAIW Scenery Library Objects FSX folder not work in P3D4? I take it no one has converted this full set of objects into P3Dv4 format?

Maybe I can help a bit here.
Key West Object Library.bgl is NOT an object placement. It is a lib that contains 49 objects and requires 25 textures. I have just loaded it into MCX and looked at it.

What you might have done is loaded Key West EZ_Objects Placement.bgl by mistake as that is a placement bgl using objects from the main lib.
The lib I loaded is from the MAIW package and is 754KB in size.

Success! Thanks to your guidance, I went back and used the MCX Wizard to do a bulk conversion of the .bgl into a P3Dv4 .bgl and popped into the scenery folder replacing the original and all the buildings are now showing up. Thanks very much for your help.

Well done! I did allude to this in the Vigilante thread, but I'm glad you got it sorted.

Appreciate your help Tim.