For some purposes it is useful to pause a running flow so you can investigate an ongoing problem and maybe try to fix it before resuming, rather than having to retry the whole flow (or from a checkpoint).
The minimal feature would be for the CPS VM to be paused between steps. This is probably an easy enhancement, with an API needed just to expose this action in the UI somewhere.
Better would be if a StepExecution (an active head) could be paused. That would be another API change. The most interesting case is DurableTaskStep.Execution; for that to work we would need to also add an API to Controller in durable-task asking it to pause the process if possible. On Unix this would be SIGSTOP (later SIGCONT); not sure if there is any Windows equivalent.