You will need to go to the existing certificate, press "Modify" which creates a new work order but with a copy of existing data, and then add the new product to the scope of the new work order.
Meaning in case of modification, it will be possible to create a new version of the audit with the same information that was filled in in the previous version. With this new version, a new scope can be assigned and a new version of a certificate can be created.
Please note that in case a certificate status was amended, e.g. suspended and reestablished, the modification audit functionality is not available. In this case, a new work order has to be created to include all information, including the new data. In case of Option 2, a new Certification Scope Work Order has to be created.