can you please expand on your reasoning for this
The stage step (and the visualization provided by pipeline-stage-view) was never designed to be anything other than serial, and there is nothing planned to make it non-serial.
There are a ton of valid usecases for needing this functionality.
Probably. But IMO this should be achieved in some other way, not by using stage. In the future we will have label (
JENKINS-26107), milestone ( JENKINS-27039) and lock ( JENKINS-30269), then we will probably be in a position to think about a solution for this use-cases.
the current visualization doesn't display that information as well as it could/should
Yes, perhaps it should, but could not - currently.
Is there documentation letting pipeline users not to put stages inside of parallel steps?
Could the visualization be enhanced to show parallel steps as "stages" in the view?
No without deep changes and it would be an ugly workaround, better to go the right way.