To Matt and all who replied --
I apologize but I misspoke - we CAN discount by % in Shift-F3. What I meant to ask was how to discuont by $ amount, and not %. In other words it is the opposite of my initial question - we simply are unable to discount by $10 or $25 off unless we create those in Price Level A, B, C. Why is there no way to simply discount by dollar amounts and only by %?