[Steve Tate]

Either wireless charging OR plugged in, if I have my DND turned on, I still get the screen lighting up when the battery hits 100% and then every few seconds after that while it's on the charger.

Do Not Disturb should be just that.

Anyone else having this and does Samsung know about it? I thought maybe Pie would fix it, but it didn't.

[Rukbat]

It's been that way since I can't remember when. If they haven't changed it now, or added a switch for 100% charge notification, they probably never will.

[pizza_pablo]

The wife and I usually charge our phones, while sleeping a dark room. Mine charges corded. Hers wirelessly. I'm pretty sure neither Note 9 does this.

[Steve Tate]

Consider yourself lucky then...

[pizza_pablo]

I consider myself fortunate for many things more than that.
I just checked and the wife's Note 9, but monitoring while charging to 100%. It did not show anything but a notification that stayed until the cord was unplugged.
No sound. No screen light up.

[bbgpsuser]

Do you have AccuBattery installed? By default it has annoying charging alarms enabled.