I have Jira Cloud with JMWE add-on.
Goal: On transition, use a post function to set a custom field (developer) to the last worker who was assigned this issue in the role (developers).
Example: I need to persist the name of the developer who most recently was assigned to an issue. I want to set that worker's name in a customer field called 'developer'. To do so, when the issue gets closed by a QA Tester (who last touches that issue), I want to get the name of the most recent assignee who was in the role called 'developers' and stuff that name into a custom field that will persist for reporting.