The idea has already been posted a couple of times, but they are archived. So lets try again. Working with inserts, like Windows, Doors, Openings etc. in Design Options is no big pleasure. When tried, Revit starts nagging about being unable to place element X in Design Option Y in a wall, floor, roof etc. belonging to the Main Model. The work-around being a copy of that host element into the Design Option. This shouldn't be necessary. Make them inserts behave like Demolished elements. When a window is demolished, the gap is automatically closed with an infill. Why not use the same method for inserts in design options?