At the moment, JIRA cascading field is not a supported field on the Create & Review screen:
Please note that the cascading-field is not displayed on the original lightning-component.
The cascading-field will appear on the beta-lightning component (https://docs.servicerocket.com/salesforce-jira/user-guide/working-with-associations/creating-a-jira-issue-from-salesforce-with-jira-issues-nextgen)
Hosting platform | Cloud |