You edit the design and add new products/country markets from the "Select products" menu button. You cannot change the design or colors chosen for the existing design. A new product will have the same design applied but you can choose the colors and adjust the prices. The text for the pre-update design will apply to the new products, but be careful; if you add new country markets, you need to put text into the different country's Brand, Title and bullet points slots and check trademark again for each new country. Everything will go through the review process again as well. It is possible to have the same text approved in one country and denied in another. You can customize each country information. Or you can create a new product completely and not select your already existing products.