UMLCn 
plantuml 时序图跨越
puml
@startuml
!include https://f.umlcn.com/c4.puml
Alice->Bob:m1
Bob->Charlie:m2
note over Alice, Charlie: 创建跨越所有参与者的备注的旧方法：\n ""note over //FirstPart, LastPart//"".
note across: 新方法：\n""note across""
Bob->Alice
hnote across: 跨越所有参与者的备注。
@enduml@startuml
!include https://f.umlcn.com/c4.puml
Alice->Bob:m1
Bob->Charlie:m2
note over Alice, Charlie: 创建跨越所有参与者的备注的旧方法：\n ""note over //FirstPart, LastPart//"".
note across: 新方法：\n""note across""
Bob->Alice
hnote across: 跨越所有参与者的备注。
@enduml