Allows for easy price settings as percentages while updating your product info in the backend. A javascript backed dropdown list appears on tab "Special" and "Discount" when price data is updated or inserted.

Demo video here
NB! this extension supports Opencart 2.+ extension installer together with the new modification functionality

UPDATE: There is now an updated functionality. Upon changing the main price - the plugin recalculates specials and discounts based on the already given percentages.

ps. vQmod version also exists just in case someone does not trust the new ocmod thing.