This would definitely be useful - especially if it was built into the Salesforce integration so the connector is prevented from creating duplicate Deals. We ran into this issue two years ago and it doesn’t look like there’s been an improvement implemented yet.
FYI there’s another idea post that seems to ask for the same thing: https://community.hubspot.com/t5/HubSpot-Ideas/deal-id-search/idi-p/15493
Thanks!