Hello Pine,
You can’t actually “remove” tilling…
The answer for your problem is here: Landscape Materials | Unreal Engine Documentation, you are looking for “Landscape Coords” node. Study that, and the grass material from Starter Pack, look at “macro-variation” comment inside the material.
Good luck!
PS: I hate it when people have been “looking all over the internet” but didn’t see their problem answered in Ue4 documentation. I believe this is the main reason most don’t answer questions here.