If you want to go back to a prior user task - and your process doesn't have built-in routing that will take you back to that task - then really the only option would be to Terminate the instance, and then restart the instance at the desired task.  This won't work if the task is inside a sub-process, only if it is in the main process.

You have to terminate it because there is a way to restart the instance at any previous user task, but that only exists for restarting it, and isn't something available while the instance is still in progress.