Question
How to use one set of nameservers for all domains?
Answer
Go to Tools & Settings > DNS Settings.
Click on a DNS record with Record type NS and click on it:

In the Name server field specify your nameserver and click OK.

The new NS record(s) will be applied to all newly created domains.
To apply the changes to all existing domains, click Apply DNS Template Changes.
Note: The Apply DNS Template Changes option is available on Plesk for Linux only.
