I think we will be releasing something specifically for this, or maybe not, it depends, We have added buildings in a different (improved) way.
Please bear in mind that depending on how you go about placing buildings in the editor you could end up not seeing buildings we have placed, or even seeing buildings that we have removed.
Also any/all future releases of the map that we're editing in Visitor will likely have a lot of changes so keep that in mind. We don't want people being angry when they've spent a lot of time adding buildings that will need to be removed later.