After I filed my return, the IRS found some mistakes in my W-2 calculations and adjusted my refund. I need to amend my return

TurboTax has changed and made it harder to do that.

Contact Customer Support to complain.

Maybe they can give you some "trick" to make it happen.

I ended up calling TurboTax customer service.

The associate checked a few things on my in-progress amended return and then let me know that there was not a way to change line 18.

She recommended sending the amended return with the unadjusted amount because the IRS would know how much they previously refunded and could perform another adjustment.

I hope this works because the previous adjustment makes the difference between a payment and an additional refund.