Cross-client customizing cannot be modified

What causes this issue?

In the logon client, any changes to cross-client Customizing objects
are forbidden.

System Response

The function was cancelled.

How to fix this error?

If you still want to make the changes, contact the system
administrator. He can allocate you a user in a client where you can
make the changes.

Error message extract from SAP system. Copyright SAP SE.