Hierarchies are not supported in more than one lead column

What causes this issue?

Planning layout '&V1&' contains more than one hierarchy. However
hierarchies can only be used, if the planning layout contains exactly
one lead column.

System Response

Planning can not be carried out with the current planning layout.

How to fix this error?

Alter the layout so that it only contains one lead column. A hierarchy
can then be defined there.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.