Viewing different locations at the same time

I have 3 different locations in my blueprint.  1) existing house  2)new hobby room/rec-room   3)main garage.  I am placing a walkway between the existing house and the Hobby/Rec-room.  They are on two different locations (elevation height differs).  I am placing a deck and stairs between to connect them with a covered walkway.  I cannot look “See” both locations at the same time.  The deck that starts from the house is only visible when I have the house location on and the deck attached to the Hobby/Rec-room door is only on when I have the Hobby/Rec-room location on.  I need to see both locations so I can connect them and place a roof over the entire walkway (decks).  How do I turn both on at the same time?