No app In App Store can handle DND, and you cannot allow one app notification to go through while all other apps are muted, even in iOS 13.
Instead, I suggest you to take down notifications of any app you don’t use that much or bombards you with notification.
People are calling for better DND for a while now. But as Apple, expect them to take years to add this feature if they ever think it is a good one to implement. 12 years for dark mode and volume hud, you get the idea.Argh... that's what I feared. But I think it would be really useful. I must wake up during my night upon reception of a certain notification coming from a professional app. But all those people texting and stuff at 1am or later...
Deactivating notifications supposes that I reactivate them each morning. Not too friendly...
Thanks for replying though.