Hi @RJCampbell,
Yes, each record in HubSpot gets a record ID. This ID can be exported and used to identify contacts which do not have any other identifier. It should appear by default in an export of company records.
Add your notes to the exported file (as per the sample file I shared in an earlier post). During the import process, you can now tell HubSpot to update the existing records in HubSpot by ID:
Hope this helps!