This is the brightness slider place you are used to, but it's not there by default with Nougat
The one everyday necessity that is gone now, is the default placing of the brightness slider and autobrightness toggle in the notification shade. It is now in the second layer of the panel, and you have to pull down the status bar once, then slide it down again to reach the rest of the toggles, where the display brightness settings are, all the way at the bottom, as you can see in the screenshots below.
It's a Nougat thing, meaning it's a Google thing, borrowed directly from stock Android, and it's pretty annoying if you are used to having the brightness slider first thing in the notification bar like with TouchWiz on Marshmallow. Well, another annoying thing is that you always have to reach the top of the phone to pull it, instead of just slide down on any empty screen area like on so many Android overlays, but that's a topic for another discussion. Fret not, though, as there is a way to bring this slider puppy back where you are used to seeing it. Here's what you need to do:
1.Pull down the notification shade once to display the quick toggles, then another time to show all the settings, including the brightness slider at the bottom;
2. You'll see a small down arrow on the right hand side of the slider, tap on that one;
3. The brightness settings should reveal a "Show control on top" toggle, switch it on, and your slider will now always be visible first thing you pull down the notification shade. Victory.