Adding Design Fees

I have a question for procurement people/accounting:

We have many vendors that we have discounts with, and we discount retail pricing for our clients. We also do a 30% design fee on our proposals because we give the clients trade pricing. However, trade pricing is not the same as our cost. I am running into this issue because we have a 30% markup (design fee) but when I use the calculator tool it will automatically put something like a 55% markup if we are not passing along cost. In our software that we use currently, we are able to separate the vendor discount and the design fee, but I am not seeing a way to do this in houzz pro on proposals. Does anybody have a solution?