While I appreciate your detailed assistance very much, the snark about "September 14 is not the best day to be learning the rules of electronic filing for a return due the next day" is not helpful. Client was supposed to provide the appraisal this weekend and I am just trying to cover all bases, since the appraisal has not yet been received.

Also, PTO does have provisions for one to easily tick a box to add the appropriate header to page 1 of Form 1120S in accordance with Rev. Proc. 2013-30 for late Subchapter S elections, so it is not unreasonable to expect the same for other items required to be stated on the face of a partnership return. 

Based upon a discussion with PTO support, the PDF attachment under 1.743-1(k)(5) will need to be made in PTO using the "defaults to main form" where one typically links an attachment to the return.