I could not find the knock knock sound in Zedge that sounded like the knock knock sound of someone knocking on a door like I had on my Galaxy Note 5.
I downloaded the knock notification from Zedge. Solved that problem
Moved from S7 to S10e .... lost the knock-knock sound. Downloaded the sound from zedge and copied to the phone's Notification folder when I connected it to my computer. Got the sound back. Thx