[sequence diagram] [autonumber] [sub-sequence] moving seamlessly from 1 -> 2 -> 2.1 ... -> 3

[rprimus]

Sun 15 Oct 2023 10:04:59 BST

Hi,

Can anyone suggest a way to do "sub-sequences" (as shown in the attached image) that does not require hardcoding the <start> numbers for autonumber? This would allow adding / removing steps (before the sub-sequence) and not have to renumber.

I've tried setting variables (!$num = #%autonumber%) and (!$num = %autonumber%), but these all cause Syntax errors:

!$num = %autonumber%
autonumber $num.1

@startuml

autonumber

a -> b : first
b -> c : second
autonumber 2.1
group subtasks
c -> d
d -> c
c -> d
d -> c
end
autonumber 3 
c -> b : third
@enduml