In any case, in the past I tried multiple methods, but nothing helps, because no matter what sub folder you will create on another partition, it will recognize once, out of two, because it is a folder native.
Now as far as I'm concerned, it's quite simply a headache of having to create subfolders and subfolders.
Indeed, that's exactly what Hartman said, and as IPACS also describes, all third party addons including airplanes should never be in the AFS2 Steam directory.
I have no addons installed in Steam AFS 2 which is in the D:
All are installed in the C: Document / Aerofly FS 2 / scenery, provided that there is enough space.
Another alternative, for those who are interested:
Those who have 2 SSD or HDD and who have some knowledge in Computing, is simply to format the largest partition and to create again the operating system in this one, which will become C: by default, and in occurance or will create the famous file in documents, AFS 2, addons ...
Then on the second, smaller (250 GB) install Steam AFS 2, count about 170 GB of free space depending on the addons you have bought and download on Steam.
That's what I did, and I'm quiet for a while!
Good luck to everyone