Not sure if this is more of a bug report or a feature request, but the mod doesn't currently scan for already generated chunks, instead starting at the center and expanding, not ignoring already generated chunks. This is very inefficient, especially if the area is already very large and you want to expand it more.

What happens currently:
Every time a pregen is started, it starts at the center and expands out slowly even if many chunks have already been generated

What should happen (imo):
Only non-existant chunks within the range specified are generated, not including already-existing chunks.

Also noticed this, potentially add a file that lists already generated chunks using the command, should make running the command more than once less painful