I think part of the problem is that Home Designer is too stupid to deal with below-grade situations. It's going to paint terrain as intersecting the house, including the open garage door, at 0" even if the area in question is essentially dug-out. And it's going to flow the terrain around the end of the retaining wall (they don't have a solid-abutting one) no matter what you tell it to do. So I probably have to redo my tri-level, built a bit into a grade, because I started with the pad, which is the first floor, at 0" terrain and floor, and have terrain that goes 14" below that and a garage pad that is basically 9" below standard ground level... but has a dug-out driveway and path for it. Instead, HDA shows grass going up the doors. Seriously. And painfully.
Dave, a few lines doesn't fix this. Please try it; you'll see.