So after I read your previous reply, I tried the landscape editing tools last night but with DataLayers in place and only one part of the landscape loaded in World Partition. So it seems to me one trick is making sure the land is assigned to DataLayers, saving, exiting Unreal then relaunching. What I did was selected my PlayerStart object and hit F (focus) to jump to that area, then in World Partition I loaded only 5x5 tiles around it. When I used the mesh tools, seemed to work a lot better to be able to edit the terrain. I’m hopeful!