Site maintainer here. There is a polygon drawing tool in the upper right corner of the map. You can use it to draw polygons on the map and assign them a height.

Site maintainer here. There is a polygon drawing tool in the upper right corner of the map. You can use it to draw polygons on the map and assign them a height. The shadows will update instantly. You can use it to add buildings that are missing from the map, simulate a tree placement or even simulate cutting down a tree if you set the height to 0.