I'm evaluating on Jira 6.2.7 sp don't know if this applies to the latest Jira, can anyone advise?
On trying to add a Regular Expression Check validator to a state transition the set of fileds available is just: Business Value, Description, Epic Color, Epic Name, External Issue ID, External Issue URL, <a local custom field>, <a local custom field>, Status Whiteboard, Story Points, Summary, <a local custom field>
What controls a field's inclusion in this set?