When building wall and roofs have holes or come our bumby. Allow the user to draw polygons on the 3D model (3SM) in the Reference model Window, across all tiles, to fix the holes and create the plane contraints without needing to export to Microstation and re-import a DGN. (as you have removed the editor license with iTwin now.)
That is a great idea. That's the tool i was looking for when using the clean up mesh tools.