When creating terrain in editor, 2 files are created in terraindata for each patches. The issue is, removing patch does not automatically deletes the files or asking for it.
It is same when deleting terrain actor itself, leaving multi gigabytes of leftover files for just a few testing iterations.
It is okay if they are some kind of backups and can be used for restoration or reimport, but I think there needs to be some kind of tracking for cleanup or delete confirmation option for human.
I logged this one on GitHub:
I’m nervous of leaving them there as I seemed to experience more terrain corruption when I was constantly recreating terrains and left them there, but that is just my opinion, no data to back it up. I don’t think they serve any purpose.