Retaining walls are the “poor cousins”. They don’t even get a Trim tab in their Properties.
Essential additional features:
Capping, centred on top of the wall and it has to step up/down with the wall (not like crown moulding in a raked ceiling . . . )
Trim options similar to normal Walls so users can show a header course (or corbel) to brick walls. Obviously both sides are external so probably the “left interior” and “right interior” just need to be left or right . . .