Thanks, Hans. Very good. That means it wasn't just my technical shortcomings

Hardly a serious bug. The waterboard, sill, frame, shutters and indication of opening are more important anyway. Also it only becomes a problem when there's a mismatch between the model dimensions and wall thickness anyway. Changing the model properties is a bit cumbersome, so I guess it would be easier if the FurnitureLibraryEditor allowed for editing all properties. But again, not really a priority issue (for me anyway - more vanity...).
And as you say, there are workarounds.
ok