Illegal knowledge base project contained in the scenario; see long text

What causes this issue?

When a template embedded specification is specified, you can specify a
business or a technical knowledge base project only when there is no
such a project in the template embedded specification.

System Response

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

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.