Migrate Started Workflow to New Version
Currently once a workflow has started, it is stuck on that version of the workflow forever. So if you find an error in the workflow, there is nothing that you can do apart from cancelling and restarting the workflow after you have fixed the issue. This is not an ideal solution in any situation, but definitely not for a long workflow.
Some ability to be able to change the course of an already started workflow would be greatly appreciated
Peter Yao commented
There is an unsupported Process Version Migration tool.