I am using the Power Apps Developer Plan to connect to the JIRA premium connector and my flow works correctly to create an issue.
However i see the new version of this action doesn't allow you to set the parent ID like the old version. If i use the Sub-Task Issue Type as suggested which is meant to give a field for parent i get an error as it's not a supported field. The parent field doesn't even appear in the configuration for the Sub-Task issue type in the JIRA settings. I had the same sort of error previously for the 'reporter' field which was listed in the issue type configuration and i was able to remove the field which allows an issue to be created.
Any ideas before I create a support case through the Power Platform Admin Center?