You can convert between sequence and collaboration diagrams. However, when you create a new diagram, you must specify that it is either a sequence diagram or a collaboration diagram.

1. Right-click the diagram background.
2. If the diagram is a sequence diagram, choose Show as Collaboration on the context menu. If the diagram is a collaboration diagram, choose Show as Sequence.
3. Repeat this process to switch back and forth.

After you convert from a sequence diagram to a collaboration diagram for the first time, or if you have added new objects to the sequence diagram between conversions, it is recommended that you perform a full layout on the collaboration diagram.