If you look at the hero image of this post, you'll notice that, despite running basically the same software, my Galaxy S6 has a slightly different set of notification toggles than my S6 Edge. Specifically, the Edge is missing private mode. Both devices are missing the toggles for mobile data and hotspot, too, which they originally shipped with. But... why?
At this point, the frank answer is that no one knows. In a problem that appears to be affecting a huge number of Galaxy S6 and S6 Edge owners, several notification quick toggles in varying combinations seem to simply be evaporating out of the drawer.
Samsung has allegedly acknowledged the issue via customer support and on a couple of regional Twitter accounts, but there's no official channel we could locate where Samsung has provided a fix timeline.
@PriMan83 Hello, our team is working on the issue.if you want the feature to return, please back the files in the phone and format the phone
Samsung's only offered solution, again, on a regional Twitter account, was to back up your important data then perform a factory reset of the phone. Some on XDA are claiming this is a software feature gone haywire, in which the OS is simply removing toggles the user hasn't touched in more than 30 days, though that doesn't exactly ring true to me given only a few specific toggles are disappearing and those who are voicing their displeasure are literally the people who use them all the time. Additionally, even though the switches do come back after a factory reset, there's no knowing if they're just going to go away again, and having to repeat this process would obviously be extremely inconvenient.
One XDA poster, NimeniAltu, has started distributing modified APKs that will re-enable the switches for Wi-Fi hotspot, private mode, and mobile data. Root is not necessary. Please note, if you use these - it is at your own risk. While they do seem to work, AP has not verified the contents of these APKs nor confirmed they will not cause additional problems on your device. That said, here's the one for mobile data (link), here is the one for Wi-Fi hotspot (link), and here is the one for private mode (link). Simply install the app, hit "add MultiWindow toggle," and the appropriate toggle for the feature in each APK should come back. You are then free to uninstall the APK. We cannot confirm this fix is permanent, so it may last and it may not. Again, use at your own risk. I will say that I tried all of them and the fix worked - all my toggles have returned even after removing the app.
We will reach out to Samsung and update this post if we receive a reply.