I have been having issues with creating a flow which updates a Creator form when a task is closed in the CRM.

The field I need to map to the Record ID in Creator is not available in the dropdown from Tasks in Flow. It is a custom field in tasks. 

This field is populated with the Creator record ID on submission of the form.

If I rewrite the workflow deluge script in Creator to populate a  different task field ( Layout_ID) with the  Creator record ID - this field IS available in the dropdown and can be mapped to the Creator record id  -the flow works and the Creator record is updated.

This makes me think custom fields in CRM Tasks cannot be mapped in Flow - is this correct?