[Imp]

Load the map in the editor
Select fill following contours of map, first button on second page
Set the fill range high so it covers the whole map, solid or your preference.
Wait a few seconds for terrain heights to be filled in then save the map.
Now edit as normal.

Saving the link is very important especially if you have adjusted the angle as you now have the infomation to fill in the map.

Being able to adjust the angle from the map screen would be a nice feature so you can adjust it a couple of degrees to see the results.
Look at long straight roads runways etc & adjust the angle to best depict them or some other major terrain feature before generating the map.
Keep in mind left right works best for deployment when rotating the map top does not need to be North.