, when you turn on DND, allow alarms. This will also leave haptic feedback enabled. Ex. you'll feel haptic feedback when you use the keyboard.
I understand why others claim that the proper use case for DND is not to prevent haptic feedback, but many people use DND mostly as a sort of "night mode," to prevent our phones from waking us with calls, texts, Twitter notifications, etc. while we're asleep. If that's why you're using DND, then this would work perfectly for you, since the only thing that'll wake you up is the alarm that you set for presumably that very purpose.
One thing that has annoyed me since the Note5 (possibly even Note4, I don't remember exactly) is the inability to suppress the LED while I was asleep. For a couple years' worth of Samsung phones I had to manually turn off the LED when I went to bed, otherwise it would flash and keep me awake if my phone so much as updated the weather app. With Samsung's version of Android Nougat, DND mode once again has the ability to stop notifications from triggering the LED. Unfortunately, the LED still stays lit with a red glow when the phone is charging, and eventually switches to green when its charging cycle is complete. But at long last, I'm once again not disturbed by an annoying flashing light at night. Now if only they could get that pesky wireless charging LED to turn off too!