If loading a BGL in the editor causes immediate freeze, check this:

This is only relevant if you have custom materials/textures in your project. This may be quite obvious for a lot of people, but I ran into this issue and Googling yielded not much help, and I discovered this by accident while rebuilding the project again from scratch. So at the cost of looking like an idiot, here’s a quick tip. If your MSFS permanently freezes (but not crash) as soon as you click “Load in Editor” for your BGL scenery asset group and all the sub-menus pop up, make sure you have loaded your MaterialLib FIRST. I had custom materials and did not click the “Load in Editor” for my MaterialLib first, hence when I loaded the BGL scenery, the sim froze. By loading in MaterialLib first, I mean wait until it is all loaded and check in the materials editor. The sim has a chance of freezing otherwise. If there are solutions around this, I will update the post with the most current and elegant solution.

Unfortunately this didn’t fix my issue, although mine is a bit different, as
when I load in my BGL my sim CTD’s once all the objects in the object window
show up. I removed the MaterialLib and ModelLib from my project and the issue
still persisted, so I have narrowed my issue down to something in the BGL. I
sent my project file to Asobo via a private comment, but I don’t think they’ve
seen it, since that post is buried under a lot of new posts. Hope this fix
works for others though!

Firstly, try putting back the MaterialLib and ModelLib. When you load
MaterialLib, open each custom material in your project, click “save”, then
close it. Then try to load your BGL into the editor. If that doesn’t work,
check your ground polygon list. Backup the .xml file, and then delete all the
entries between and . See if the problem is resolved.

Both those solutions definitely helped, because instead of CTD’ing
immediately, I was able to move the camera around for around a minute,
however, unfortunately it’s still crashing.

Update 2: I have narrowed down the issue to either the taxiways or the parking
spots. The project works perfectly without them, so my issue is completely
unrelated to the MaterialLibs then. I’ll probably just end up redoing them
(since I didn’t make much progress anyways), but thank you for the help!