It doesn't matter, since the deduction has not been extended by Congress to cover the 2018 tax year. It was left in the program "just in case", but I don't think Congress and the President are in a cooperative mood this time.
I think the answer is yes, that's how you would have to do it, because Turbotax doesn't have a place for "Additional mortgage insurance premiums." You can enter the amount and, IF the deduction is turned back on, it will be added to your tax return.
