To create horizontal links between Diagrams you must reuse the same Business Event across diagrams. You must ensure the Business Event that ends one Workflow Diagram is the same one that begins the next Workflow Diagram. Once Activity Paths link to the Business Event in one diagram and links from the same Business Event in another diagram, a link will automatically be generated in both diagrams.
For more information, see QualiWare Starter Course, Lesson 6, Topic 1-5