Sequence: Long Block Tab And Divider Labels
Long block and divider labels over adjacent participants: the gap between the participants widens so the label ends before the next lifeline.
sequence-long-block-tab-and-divider-labels.mmd
sequenceDiagram
participant A
participant B
par a branch with a long descriptive title
A->>B: x
and another branch with an equally long title
B->>A: y
end