I'm still on Kitkat, so I don't know the abilities of LP on your S6. Given that, in Kitkat, there is no way to alter or add any Quick Settings features. The best I can offer as an alternative is to install
QuickShortcut Maker. It can't add to the Quick Settings menu, but it can make direct shortcuts to app activities and place the shortcut on your home screen. You can rename the shortcuts and also change the icons. If you have icon packs on your phone you can use them in QSM.