In Pega 7.1 case designer, stages had steps, and each "step" represented an entire process flow. When configuring "step behaviors" one could say it is a single step assignment, or multi step process. When choosing the latter, the system merely placed a second assignment within the flow rule, whether or not that shape would remain or be deleted. There was technically never a need to use the step behavior drop down menu in Pega 7.1. It was a nice idea, but in truth if you went directly to any flow rule and added a second shape to a single assignment process, or deleted the original assignment shape and replace it with an automated shape, the step was still marked in the case designer as a "multi step process."
In Pega 7.2 case designer, stages contain processes, and processes contain "steps". "Steps" are analogous to the shape it represents within the process flow. So the concept of single step process and multi-step process are still supported. It's just done in a more straightforward manner.
I hope this helps to explain the difference.
For more information, you might find the recently released Pega Academy self-study course Leveraging Pega 7.2 for System Architects beneficial. It is a free course and covers content that is not covered in the SAE I and SAE II v7.1 courses.
I am working on the Pega 7.2 Senior System Architect class and I have noticed that if the main process flow for a stage is edited by adding say the Split For Each Shape, Pega then deletes all of the steps from the stage and removes the Add Step button. The process still works and can be edited as a whole but the view of each stage as a series of documented steps is gone. From this point on, there is no ability to add steps to the stage though I can continue to add shapes to the stage process flow. Is this the recommended design approach in 7.2? Should I now avoid breaking a stage into individual steps and just edit the main flow? Continue to break a case into stages but instead of using steps, just have one large process flow or maybe a few large process flows per stage.
You are correct when adding any step to the flow that is not a Collect Information, Approve/Reject, or a SmartShape the Case Designer removes the steps and forces you to create the flow manually. While the Case Designer is great, you can see it has some limitations. So when you create more complex processes, i.e. ones that include more advanced shapes or decision shapes the process will remove the steps in the Case Designer. You can still modify the flow and will have to going forward if you would like to add something to that flow.
The idea is group like minded tasks together when creating your processes. You need to take into account if those processes run sequentially or in parallel. Is there an occasion when you can skip a process or processes?
At any rate the Case Designer gets us started and when we need to get a little more complex we are left to configure the flow rule directly.