For those who have the same issue - you find this article, but the link no longer works, plus this is also not easy to search for in the documentation, and this is nowhere in the Setting or Views tabs of the Snap - you may waste hours trying to figure this out. You just want the answer:
The document output circles can be directly connected to other Snaps by dragging and clicking on them until they go from white to blue. Alternatively, if you want to connect Snaps that are not near each other on the UI canvas you click and hold the white circle - as you start to drag it it will turn yellow - then drag this to the Snap you want to connect to. When connected a reference number will show the link. This is the same as a direct connection.