Retaining wall excavation/dumping

Allow trucks and escalators to dig or fill land on both sides of a retaining wall which will allow a smooth, level finish on both sides.

You can call "toggle_terrain_designations_over_entities" in console, which enables you to make designations over retaining walls. It is off by default because you can easily undermine/overfill them and destroy them, if you are not carefull with designations.
Should be definitelly a normal option though...