Hopefully, you are using a desktop version of TurboTax because you will have to resort to using Forms Mode.

Regardless, you might want to contact Support tomorrow.

What is the TurboTax phone number? (intuit.com)

I figured out how to do it. The following answer is for the benefit of others with the same problem.

1) Go into forms mode. (Requires TurboTax Desktop.)

2) Find Schedule C for the business that earned the income that is listed in the 4797.

3) Scroll down to the section of Schedule C, named "Qualified Business Income Deduction Smart Worksheet".

4) Go to line "E2, Adjustments to qualified business income".

5) Type the income from 4797, into this adjustments field. The income should now appear in the associated QBI worksheets and calculations.

6) Click through the Schedule C section one more time in interview mode. You might or might not be prompted with new questions after changing the form directly.