Are you preparing a 1065 or 1040?  Assuming you are preparing the K-1, Supplemental Info for Line 20 is entered on Screens 30 and 31.

There are proper codes on Line 20 for everything related to §163(j).  Why would the partners need ATI from the partnership?

I AM ENTERING FROM PARTNERSHIPK-1 LINE20 STMT AH TO 1040 INDIVIDUAL.

Line 13 Code K should be entered on Screen 20.1 under the Line 13 - Other deductions section by selecting K-Excess business interest interest from the K-1 Code column.

Line 20 Code AE and AF for Excess taxable income and Excess business interest income would be entered under the Line 20 - Other section, on the lines for (20AE) Excess taxable income and (20AF) Excess business interest income.

If there is any supplemental information for Line 20 Code AH, you will need to determine whether it's relevant and, if so, decide which form or schedule that piece of information may belong to.