I was able to set the Assignee to "John" via Scriptrunner.
My next step is to set the Assignee to "John", but only if the Assignee field was left as Automatic by the user. If the user enters or selects a specific user for the Assignee field I want to honor that. This does not work:
issue.get("Assignee")=="Automatic"It is true I could use the Component lead for a similar effect, but this particular project does not use components.