I'm surprise that a basic 'duplicate' or 'clone' button isn't available for the Sales Team when creating 3 or 4 deals that are almost the same. In our case the Sales Team create 3 or 4 deals with the same company and aren't happy on populating 15 fields all over again and again.
HubSpot support suggested using a 3rd party widget (revLABS) that adds a 'Duplicate Deal' button but when I click on it made buy a subscription to get this working accross our organisation and because is a 3rd party software, HubSpot won't provide any additional support on it.
I'm surprise this isn't a priority item for the Dev Team. This is just basic functionality for Sales Hub. We moved from Salesforce to HubSpot and the Sales Team are screaming to see the 'clone' or 'duplicate' opportunity/deal button we used to have in Salesforce. It's difficult to explain to my Management Team why there isn't a duplicate option available on HubSpot. Keen to hear any feedback from the HS Team on why this hasn't been put on the roadmap yet so I can share this internally.
After you enable the 3rd party integrationMessage when you click on Duplicate Deal