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For the report-type Issue → Sub-Task, to include the issues without sub-tasks, select Include issues without sub-tasks.
For the report-type Issue → Linked Issue, Epic → Linked Epic → Issue, and Issue > Linked Epic > Issue,to view the link type, select Include link type.
The Report Designer Interface provides help text for each report type. To know more about how the various report types work, navigate to report-specific help text:
How does issue-subtask report work?
How does epic-issue report work?
How does epic-issue-subtask report work?
How does issue-linkedissue report work?
How does epic-linkedepic report work?
How does issue-linkedepic report work?
4.To view the required fields in the report, addthe fields from the left panel by clicking ‘+' sign next to the field name. The fields list contains all standard Jira fields, custom Jira fields for the instance, and calculated fields created using Reports and Timesheets for Jira app. The fields with an 
symbol are explained in detail here. Fields can be dragged and dropped in the Fields section to rearrange the columns.
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