Density from 0...1
Y Position from 1..0
Left mouse click to add points, hold left mouse to drag a point
Right mouse click to remove a point

Yellow points are less then 1 block apart vertically from the previous point and might not contribute anything to the landform
Blue line is the default sea level
Light gray line grid dimension is 5 blocks

landforms.json Y-Key-Positions / Key-Thresholds (paste/modify to update graph)