Skyways
You can do this for visualization and conceptual design purposes by sketching a design road that connects between two buildings, and then Add a Bridge to that design road.
If you stylize the road to be a pedestrian walkway or something like that, you can add 3D model decorations to the bridge deck style (i.e. road style) as well, such as fences, barriers, etc.
You may have to move the buildings to cover the abutments (you can delete one abutment, but not both), and also may want to experiment with facade styles for your buildings in order to get your doorways to line up with your skyways.
Here's a rough example that I quickly sketched. However, note that the bridge actually extends into the middle of both connecting buildings, so material quantities of the bridge and/or road will not be accurate.
