Sequence diagrams have special shortcut syntax to deactivate source, or to activate target. However there is no syntax which would allow to perform both. This would be helpful for diagrams with multiple participants, which performs some action in response to incoming message, and then forwards it to next one for further processing.
For example there are multiple participants which forwards message to next one:
A -> B: Msg
B -> C: Msg
C -> D: Msg
It would be nice to be able to specify multiple shortcuts to express this, e.g. "-- ++". This should also work with ** and !! - e.g. allow to use "-- ** ++".