Where has the notification folder gone?

[AC Question]

I have used my own notification tone for years, no matter what phone I had. I was even using it on my S6 until the last update (6.0.1). I got a message and it used a regular tone. When I went to add my own to the notifications folder, the notifications folder wasn't showing in my files. Is there something I'm missing, or has the option to add your own notification sounds been removed?

Just to add, I can still add my own ringtones. That side of things still works.