Need help with 2022 MD Fiduciary return, final diagnostic says to add a code to the end of 504 form, but in forms mode, I found no such box. Need help to find box?

Diagnostics says "if you complete Form 504UP..., and have no interest due, attach Form 504UP to your fiduciary return, and write code number "301" in the box marked code number, at the bottom of Form 504...be sure to attach Form 504UP, even if there is no interest due." Does anyone know how to find/access this 'box maked code number' to add the #301?