You can hide the domain name registration and domain management buttons both through the command line and the Partner API.
To remove the Register Domain Names button and Manage Domain Names button using the command line, run the following command:
plesk bin panel_gui -p -domain_registration true
"%plesk_dir%\bin\panel_gui.exe" -p -domain_registration true
To remove the Register Domain Names button and Manage Domain Names button using the Partner API:
partner10.upgradeKey with the API identifier "EXTRAS_BUTTONS_OFF" in the "array of identifiers of upgrade plans" parameter.
For details on these methods specification, please see http://central.plesk.com/docs/partner-api/1.0, section Specifications of Methods / partner10.createKey
Note: API identifier "EXTRAS_BUTTONS_OFF" also disables the controls related to SSL/TLS certificate selling services and the link to the provider's website.
Important: Once you have turned off a feature through the Partner API, there are no documented methods to turn it back on. If you need to perform this reverse operation, please use the web-based user interface, or contact your sales representative.