But if you have rotated your terrain and then want to change a small part of it. Then what?
I followed one of your tutorials on making an island and I turned the island around until I got a good scene, but I wanted to remove a large mound that was in the way. When I went into the Terrain Editor, I couldn’t work out which bit I had to alter as there were similar mounds around the edges.
OK, right, what you can do is this.
Use Edit > Copy Matrix on the terrain you want to edit.
Then reset the terrain orientation by clicking on one of the control points while holding down ctrl + alt.
This will then align the terrain in the scene so that you can place your camera over it (point your camera North as shown) - save your camera position first - before moving your camera.
You will now be in a position to look a the terrain as shown above - with known orientation.
Once you have made your changes.
Use Edit > Paste Matrix to restore your terrain back to it’s original orientation.
And restore your camera position with the camera dot.
A bit fiddly I know…