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As you can see in the above screenshot, complete type hierarchy is reflected to the timesheet view from Initiative to sub-task.
Don’t confuse “Parent Issue” with field value grouping “Parent”. “Parent” grouping only group issues for their direct parent. It doesn’t show complete hierarchy. For example, for the above data “Parent” grouping will produce the following report.
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As you can see, above report has only 2 level hierarchy. We have also added “Parent” as field so that, you also see that even the top-level issues have parents. For example, TEST-108 has parent TEST-114.