Can I create another dummy tax return with different input to better determine what my estimated tax payments should be for 2019.
How do I do that?
You would have to use a new online account. Or use the Desktop program. You don't have to pay unless you want to print it.
Online is only good for 1 return. But you can use the same email address for 5 accounts. How to start another return in the Online version https://ttlc.intuit.com/replies/3288574