Show everyone who worked on the task

ARRAY(reporter, assignee, developer, tester)
CODE

Note: developer and tester are custom fields - they will be automatically mapped only if those custom fields exist in your Jira instance.

Show everyone who worked on any task in the subtree

VALUES { ARRAY(reporter, assignee, developer, tester) }
CODE

Note: developer and tester are custom fields - they will be automatically mapped only if those custom fields exist in your Jira instance.