It's been a while since I worked on anything with FSX, but this should work the same since it's ADE. I'm using version 01.78.7298.19731 when you click on "about" up at the top ribbon.
If I'm understanding correctly, you just want to keep the default airport for now with a new ICAO code. The following SHOULD work:
1. Open the 11J airport in ADE. I took it from the default airport option where you search for ICAO 11J.
2. We'll test with the default airport for now, but it should be the same with any changes down the road.
3. Select "File" then "Compile Airport" in the drop down menu.
4. In the options dialog click on "More Options" near the right side.
5. In the new window click on "To Specific Folder" both times and select a folder for your project. I usually have a separate folder in the project folder for messing with xml, which is what you are going to do.
6. Ensure the "Compile Separate Airport and Object Bgl Files" and "Compile Airport and Scenery" options are selected/checked.
7. Close and compile.
8. Go to the place you compiled and rename the two bgl to something that makes sense to you. "KBIJ_ADE_V1.bgl" and "KBIJ_ADE_OBJ_V1.bgl" for example. Do the same for the respective xml files.
9. Open the "KBIJ_ADE_V1.xml" up in an editor. I use Notepad++, but regular notepad is fine. This is something simple, so the extended xml editor functions are not needed.
10. Change the ident="11J" to read ident="KBIJ".
11. Ensure all the "DeleteAirport" entries below it are set to TRUE and save.
12. Open the "KBIJ_ADE_OBJ_V1.xml" file and ensure you have all the exclusion rectangle information still in there. No need to modify here for our purposes. Just make sure the entries all have a "TRUE" entry at the end of each section to delete all objects.
13. Now you will need the SDK for the scenery. Copy the "bglcomp.exe" and "bglcomp.xsd" from the SDK over to the folder where the bgl and xml files are.
14. Select both xml files one at a time and drag and drop them individually onto the "bglcomp.exe" file and let it run. You should get a black box flicker on the screen each time.
15. Check each of the bgl files and they should have a current time-stamp meaning they were just created.
16. Copy these files to an active scenery folder that's higher than default and see if that works.
Not sure if this process will work in FSX, but FS9 it SEEMED okay.
If you're making a new airport from scratch, then the takeaway is that you need to export the xml files every time you make scenery to ensure the "DeleteAirport" entries are all TRUE since you want to replace whatever is in the default sim with what you are making in the current scenery project. Sometimes they default to FALSE.
As an example, you'll have an ILS or a VOR approach at an airport you regressed to classic or vintage era status. When you look in FS, the ILS and all navaids are still there even though the ILS itself was deleted in ADE. That's because ADE actually replaces it with a water runway option. You then have to go into the xml file and manually delete the approach in the "DeleteAirport" section by setting it to TRUE, and then farther down the document you have to delete the whole entry as well. You then recompile with the drag-and-drop method in order to truly not have it in the sim.
That's just one of the many things you can do with the xml post editing of a file, but there are more. If you know the GUID entries, you can clear them out from the xml for the object files as well to make sure they don't appear.
With the FSX option for ADE you can do terrain features as well, from what I understand. This means you can add an exclusion rectangle for other things like landclass, and you can also combine all the stuff with the airport skirting and grass so that it's one CVX file. This is something I do for FS9 with SBuilder9.
Not sure if this fixes your issue, but it may help with other stuff down the road as well.
Hope this helped and let us know if it worked for FSX.
Regards,
Jorge
Miami, FL
PS: This is IN ADDITION TO what Dan just posted as I was typing, and should be done afterwards to ensure the airport and/or ILS's don't show up as the tutorial states they will.