Lets be very clear about this.

Quickbooks Online is a massive backwards step from Quickbooks Desktop.

Quickbooks Online costs a lot more but fails to provide many of the basic features found in Quickbooks Desktop.

People have been asking for the ability to customise  Purchase Orders and other forms for at least 12 months. If Quickbooks was committed to customer support they would tell you when this feature was going to be available, not ask you to submit Feedback.