TurboTax wants Form 5329, Line 7 - Excess traditional IRA contribution credit entry. In 2023, accidentally entered 401K as IRA contributions. How to correct?

The way to correct this is to file an amended tax return. You'll need to remove the deduction that was taken from the IRA contribution. You can amend for 2023.

You can answer the question in the 2024 IRA entry section that you did not have any excess contributions in a  prior year.

Per How do I amend my federal tax return for a prior year?, here is how to file an amended return in TurboTax Online:

1. "On the Tax Home screen, scroll down to Your tax returns & documents and select the year you want to amend.
2. Select the Amend (change) return dropdown, then Amend using TurboTax Online. If you're told to amend your return via TurboTax Desktop, follow the steps for TurboTax Desktop instead.
3. Continue through the screens, make the changes you need to make, and carefully answer the remaining questions to finish amending your return."