How can I edit the Nonresident / Part-Year Resident Ratio Schedule?

If you are using a version of TurboTax Desktop, then you can enter information directly on the tax form by clicking Forms at the top of the screen.  This will show you a list of all the forms and worksheets being used in your return.

There will still be fields on the forms that do not allow direct inputs, so you have to be careful about what you are doing.

Be aware that overriding and fields or calculations using Forms mode will void the TurboTax Accurate Calculation Guarantee.

There is no method to allow you to edit any tax forms directly if you are using TurboTax Online.