You can change the domain name registrar's URLs only through command line.
To change the URL of the Register Domain Names button to "https://www.example.com" , run the following command:
plesk bin panel_gui -p -domain_registration_url https://www.example.com
"%plesk_dir%\bin\panel_gui.exe" -p -domain_registration_url https://example.com
To change the URL of the Manage Domain Names button to "https://www.example.com", run the following command:
plesk bin panel_gui -p -domain_management_url https://www.example.com
"%plesk_dir%\bin\panel_gui.exe" -p -domain_management_url https://example.com