It would be great to be able to test individual actions in the workflow designer without needing to run the workflow test.
An example of this would be if you build an API call using the Call a Web Service action, it would be good to be able to test just that action to test the API call, without needing to run the whole workflow test (or have a workflow test sitting in that state).
Another option would be the ability to trigger actions to re-run from the workflow testing screen. Issue here is that I have a large workflow, and an API call happening part way through. If the API fails, I can't just tweak it and run another test, I need to re-run the full workflow.