Samsung has come out with QuickPanel Restore, an app with the only purpose of adding the toggles for quick settings back to the notification panel. Upon restoring the toggles, an option is provided to uninstall the app immediately.
According to Sammobile, Samsung has remained silent on why some Galaxy S6 and S6 Edge devices were affected. Nevertheless, this is still good news for those who desire these toggles and want to get them back.
In order to receive the app, go to the Galaxy Apps store on either aforementioned device, and search for QuickPanel Restore in order to download it. You can also click this link to take you right to the page.