I am not sure why this is marked as resolved, all the Proposed solutions required workarounds using workflows, and or using third party solutions to enable this functionality, where it is a basic tools to be able to duplicate deals. This can be for re-curring orders, orders of similar types etc and this should extend to line items as well.
I need my sales team to be able to copy deals quickly, and without going into areas of Hubspot that are not relevant to them. It is not the role of my sales team to do this, nor should I have time in our sales operations . enablement to have to do this amount of work everytime to copy a deal.