Can we have an option for modifier items to charge a percentage of the menu item price? For example, if "bourbon" is priced at $10 and "vodka" is priced at $8, we could add a modifier item called "neat" and instead of charging a fixed amount, it'll charge 50% of the menu item price. So in this case, the charge for "neat" would be $5 for "bourbon" and $4 for "vodka."