The "Shared PC" policies in the Windows Configuration Designer (WCD) may not be available if you are using an outdated version of the Windows Assessment and Deployment Kit (ADK) or if the policies have been deprecated in the latest version of Windows.
Checking the Microsoft documentation for the latest information on the availability of Shared PC policies in the WCD will be helpful and make sure you have the latest version of the ADK installed. If the policies are still not present, you may have to use other methods to configure the shared PC settings, such as using Group Policy or Windows registry settings.