To create a new loan contract for a customer first click "Loan" on the right of the customer summary section.
Customer details which are pre-filled are the same as those in the customer section. However, other details such as income and expenditure need to be filled in. To duplicate all details, click the "Reloan" button instead, but note that it's not for refinancing. It quickly creates a new loan with the same information as a previous one, without establishing any connection to the original contract.
For more information about the process of creating a new loan contract: