In the Custom Scenery folder is a file named scenery_packs.ini
If you open this file with Notepad you'll find a list of all the scenery installed in your copy of X-Plane11
The order of this list is vitally important
From the bottom up, the list should mimic how the scenery is built...
At the bottom is the mesh
Then comes the Ortho tile which covers the mesh
Then Global Airports (The default airfields supplied with each new version of X-Plane11
Then your Ortho4xp Overlays
Then Landmark and Aerosoft
Then add any 3rd party libraries
Then at the top of the list comes all your Custom Airports.
The higher entries "cover/obscure" everything lower.
Simply Cut n Paste
Hope this helps