First try: Pressing 'x' while clicking or dragging with terrain 5 at the cursor. No success.
Second try: I select terrain 4 (water) and want to place it instead of the rock corner. But neither clicking nor dragging works.
Third try: I select terrain 6 and want to drag it from outside the water to the rock corner or simply click at the terrain 5 rock corner, but in vain.
Fourth try: I select terrain 1 (the old rocky mountain). Now, when I click or drag on the terrain 5 part I want to delete, the corner is replaced by a terrain 1 tower, but with some strange side effects (some terrain 1 rocks appear around the water near the deleted corner).
I tested this one level higher, too: If I place a terrain 4 lake on top of a terrain 5 mountain and in that lake a second terrain 5 mountain it's very difficult to delete a part of this upper rock.
Expected behaviour:
Deleting of terrain 5 blocks should be possible in the same manner as with normal rocks by holding 'x'.
