I’ve done more troubleshooting and found that this crash/bug appears to have something to do with “Enable Edit Layers” feature during import. I started over from scratch and imported everything without “Enable Edit Layers” selected. This time, I can load many tiles and move them about in the World Composition panel without any issues.
But by not choosing to enable edit layers, I’m concerned I won’t be able to properly edit my landscapes. I’ll keep playing around and see what happens. Would love feedback from someone with more knowledge on the subject to chime in. Thanks!