After playing with it for a while, I think you enter the toal QBI income on section D1, then you can enter the deductions (such as SEHI) on D2, section E, line 5.
If I remember correctly, although I think the IRS said SEHI for an S-corp is taken out of QBI, many people feel that logically that is incorrect. But it's been a while, so my memory is a bit hazy on the subject.
