By Daniel Kline The fast-food giant has jumped onboard a trend that might be the next big thing or it might flop. Earlier this year McDonald’s (MCD) – Get McDonald’s Corporation Report added some secret menu items to its actual menu. It was a sort of brilliant move because it let the fast-food chain promote new menu items without actually adding any new ingredients. That’s a page straight out of Yum! Brands (YUM) – Get Yum! Brands, Inc. Report Taco Bell’s playbook where you use the same palette of ingredients to make lots of different menu items. McDonald’s take on it, called “Menu Hacks,” off…