You are trying to build hierarchichal relationship in reports between custom KUT fields created.
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- Hierarchy cannot be supported in the KUT fields because it needs special coding to work in hierarchichal manner provided by the standard application teams who are responsible for the work center screen in which the KUT field is added.
- The Application teams will develop such code only for standard fields provided by SAP.
- You cannot enable Hierarchy in reports for custom KUT fields.
- Hierarchy can be enabled only for standard fields like Account, Territory etc provided the respective application teams have enabled hierarchy.
To know more about Extension fields refer to the below help center document.
Hierarchy, Reports, KUT Fields, Custom Fields, Extension Fields, Enable Hierarchy, Parent, Child, Relationship, Levels , KBA , AP-RC-ANA , C4C, ByD, Travel: Analytics Tools & Frameworks , How To