If we have a single flow with multiple assignments we can move back and forth between assignments using flow actions, e.g. approval sends the flow ahead, reject can go back to previous step, cancel can keep the flow on the same assignment but closes the window. etc... But when we configure the same design using case designer, how can we go back and fourth among multiple steps?
As its stands I don't beleiev you can. The wizard will only get you so far and then ... well then you're into exactly as you described things, flow configuration, flow actions like Previous and Back, Jump to Stage shapes and beyond (ScreenFlows). Think of the Case Designer as like Launch control in a race car. It'll get you off the line and up to 60mph in a heartbeat, but it won't drive the car round the track and win you the race ..... yet :-) It's constantly being refined and improved but, its still a fairly young feature...
Pega says each step defines a Task(Single Step), a Process(Multi Step) or a Case.
So if I want to design my mentioned scenario then I should go for a step with a Multi Step Configuration, and going back and forth among different flow actions will become a part of that Multi Step. a.k.a Process.
A step should be configured as a single step, only when that task is an independent task and not part of a bigger process.
The tasks of a bigger process cant be defined as a collection of single steps in case designer, for it will be nearly impossible to move among those takss.