I don't have a mobile data button in the quick settings panel. I know how to access the mobile data via the system menu but why press multiple buttons for a function when you only need one. (first world issues are rough lol) If you go into the edit feature of the quick settings panel still no mobile button.
PS: Had some issue with a LG product and switched to the S5 neo. I actually have cell service again, the LG was disappointing.