I got an s10 a few months ago and was inconvenienced by the fact the notification light feature my s7 had was no longer there so I ended up using an app to wake the always on display when there is a notification. 

I now have an iphone 6s as a second phone and am fighting the same battle. Not sure why manufacturers make features so stupid when the basic function of a phone is to alert you when someone wants to contact you. 

So if I leave the room for a minute or have a shower or something how do I make my 6s notify me there is a missed a message/text or call?

Currently the screen lights up for a few seconds and the led flashes a couple of times, then there is no sign of the alert, nothing to tell me I missed a notification, until the repeat alert kicks in (which has a max of 10 repeats). I don't want to have to press the home button on my phone to see if I missed anything every time it has been out of my constant vision for more than 1 second. So if I am away from the phone for 20 minutes (10 repeats at 2 minutes) there is nothing to notify me without manualy checking it? Not good enough. 

Is there a way to keep the screen on or led periodically flashing until I clear the alert? or is there a way to have a repeating audio tone until I clear the notification?