&1 object type cannot be changed to master category

What causes this issue?

This object category cannot be changed to a master type. Dependent
entries are maintained in the sub view and belong to an associated view.

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

System Response

How to fix this error?

Please delete the existing entries in the sub view (associated view) and
change the category type before changing the category.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.