Right-click the DL and drag it a little way in your Contacts folder.
Release the mouse button and choose Copy. Thie will create an identically
named DL containing exactly the same members. Open the copy, give it
another name, and remove some of the members. Close and save. Open the
original DL and remove the members you did NOT remove from the copy,
retaining the members you DID remove from the copy. Close and save.