About model and data exchange with 3rd party solutions: Revit, Solibri, dRofus, Bluebeam, structural analysis solutions, and IFC, BCF and DXF/DWG-based exchange, etc.
For Plateau's that are right next to the retaining walls this is what I do, and actually the angle seems to max-out at 89.9°.
For Plateaus that are cut some distance from a retaining wall, I would like any digging or embanking to "stop" when it reaches the retaining walls location.