Only make changes in the permitted namespace

What causes this issue?

The message destination whose target fields you want to change starts
with <LS>PI</>. This means that it is within the name range reserved
for SAP.
Your cannot make any changes.

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?

Error message extract from SAP system. Copyright SAP SE.