ADE files are airport construction files. They should be in the scenery folder of the airport they belong to. The ADE file name should include the name of the airport, or ICAO code in it. They can be placed in the scenery/global/scenery folder, scenery/world/scenery, or Addon Scenery/scenery folder, but that physically separates them from the files containing the surrounding scenery objects of the airport the ADE defines. It will work, but is not ideal. (my 2 cents.)