You can organize sequence diagrams to better represent a system.
You can reorder messages, delay asynchronous messages, as well as manage combined
fragments and lifelines.
Reordering messages in sequence diagrams
In sequence diagrams, you can move a message across other messages and interaction fragments on the same lifeline or on another lifeline to reorder the sequence the messages occur. After you reorder a message, the message number automatically indicates the updated position on the lifeline.