Hi PlantUML team,
When creating complex sequence diagrams with a lot of participants and lots of messages, diagrams tend to take up a lot of space, both horizontally and vertically. This simple example in Puma:
@startuml
autoactivate on
participant Alice
box "Grouping" #LightBlue
participant Bob
participant Charlie
end box
participant Dave
Alice -> Bob : request
Bob -> Charlie : request
Charlie -> Dave : request
Charlie <-- Dave : response
Bob <-- Charlie : response
Alice <-- Bob : response
@enduml

Already takes up quite some vertical space.
With Teoz it takes up minimal space:
@startuml
!pragma teoz true
autoactivate on
participant Alice
box "Grouping" #LightBlue
participant Bob
participant Charlie
end box
participant Dave
Alice -> Bob : request
& Bob -> Charlie : request
& Charlie -> Dave : request
Charlie <-- Dave : response
& Bob <-- Charlie : response
& Alice <-- Bob : response
@enduml

Note the small rendering artifacts there, but nevermind those for the moment.
This diagram now kind of lacks the "sequence" look 'n feel :'(
So, would it be possible to add a small vertical offset to make it look more like this mspainted example:

Perhaps configurable with a skinparam? Or using the ||42|| format?
I hope Graphviz's ranks are not blocking this move :p
Thanks for all the hard work!
grtz,
Jurgen