Class/Interf. &1 contains stored procedures, cannot be changed in SAP GUI

What causes this issue?

Changing classes/interfaces containing ABAP Managed Database Procedures
is not supported by Class Builder (in SAP GUI).
The class/interface &v1& implements or comprises the interface
IF_AMDP_MARKER_HDB. This means, it provides the option to add ABAP
Managed Database Procedures to the class/interface.

System Response

Class Builder remains in display mode.

How to fix this error?

Use ABAP development tools for SAP NetWeaver (ADT) to edit the
class/interface.

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.