I am looking for something similar but would love to be able to pass in a Deal Id in the API when creating a new Deal in Hubspot from a downstream system that has already generated the unique idea used across our enterprise. We currently pass this in as a custom property on the deal object but it then allows for duplicates in HS API submission (and you cannot search for a Deal by our custom property). Ideally our own Deal Id would be sent in the Deal Create API call into HubSpot.