By default from the Jira's behavior, the Resolved date should be cleared (null) when the issue's Resolution changed to Unresolved. Screen Recording 2020-10-06 at 8.16.42 PM.mov
- Create a new issue
- Transition issue to Done
- Use the ScriptRunner built-in feature 'Bulk Fix Resolutions' to set the 'Resolved' resolution to 'None'
- Resolution set to Unresolved and Resolve date cleared from the screen (null)
- Resolution set to Unresolved and Resolve date remain the same value