TurboTax helps states the following: To amend a past return, follow the steps below 1. 2.3. 4. Select Amend (change) return But there is no such option.

Turbotax help states the following.
Your TurboTax return for this year hasn't been filed and accepted yet, so you can't amend it. You can continue to make changes to it before you file though
To amend a past return, follow the steps below
1. Select Tax Home from the menu on the far left
2. Scroll down to Your tax returns and documents