The input is on screen #42.271, the last item in the MISCELLANEOUS section.  The input line is called "Overpayment applied to next year (Form 511).  (I have no idea why the input isn't on screen #10.)  In the S-corp module, you can select 1 to apply all, but in the 1065 module, yo must enter the exact amount, so be careful.  Also, the overpayment applied is not currently being taken into account when the program calculates the 2021 estimates needed, and it's not reflected on the instruction letter.