How can I add extra principal payments to a Mortgage?

This question was taken from the email list archive and there appear to be two answers.
The first option is to record the transaction as normal and then add a split that goes to the
loan with the extra principal amount. The second option is to add the extra principal to
mortgage amount. In either case, MoneyDance should handle all the hard stuff, such as
calculating your next payment correctly, adjusting the remaining number of payments, and
anything else.