You mean cover only the top layer so that everytime you run by it makes the nearby cave noise? You got it boss!

Fine, but since there isn’t enough dirt to fill it in I’m going to make a bunch of floating trees and fill it with wood :)

I like to keep one valley not patched so it looks like place where many battles took place

I myself like using a mod so that it automatically repairs itself

Or embrace the hole and make it a perimeter

/gamerule mobGriefing false

But leaving it alone adds environmental story telling for future explorers.

Or you can make it a little pond.

/set gamemode 0

FTB Chunks user: you have no power here.