Making notification sounds quieter on a non-rooted FP5

Hi all, I've had my FP5 for a few months now. I usually have my notifications on vibrate only, simply because I think even the lowest volume level for notifications is too loud.

So I'm wondering, is there a way to go below the lowest possible volume for notifications somehow, and preferably without rooting. Or should I try my luck making a feature request at Fairphone?