Changing ABAP Managed Stored Procedures is not supported in SAP GUI

What causes this issue?

Changing classes containing ABAP Managed Database Procedures is not
supported by Class Builder (in SAP GUI).
The class &v1& implements the interface IF_AMDP_MARKER_HDB. This means,
it provides the option to add ABAP Managed Database Procedures to the
class.
You forced Class Builder to allow changes in class &v1& because you
defined the parameter SEO_SOURCEBASED_AMDP in your user settings.
This mode is intended for support use cases only.

System Response

Class Builder allows changing class &v1& because you defined the
parameter SEO_SOURCEBASED_AMDP in your user settings.

How to fix this error?

Remove the SEO_SOURCEBASED_AMDP parameter from your user settings and
use ABAP development tools for SAP NetWeaver (ADT) to edit the class.

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.