Automation rule to create multiple subtask based on user picker (multiple users)

[Helen]

My issue has a "User Picker (multiple users)" called "Reviewers". I'd like to write an automation rule to create a subtask for each user in Reviewers and set that user as the assignee.

I have written a manually triggered rule which works when there's only one person in the Reviewers field. However, I need to be able to iterate over each user I think, and I can't work out how to do that.

Any suggestions for Jira Data Center would be gratefully received.