Ah, maybe I should have clarified. While I've taken some care to curate the notifications I get on my phone, there are nevertheless times that Twitter, Facebook, Gmail, etc... would just be a nuisance. When I'm meeting with someone, the buzz of my phone is distracting to me and strikes me as a little rude to the other person (we both know I'm thinking about that buzz, and I want to be completely present in that conversation), which is why I tend to enable Do Not Disturb mode when I'm supposed to be engaged. The problem is that some notifications are valid to let through - in particular, a reminder that I have an event in 15 minutes (particularly a one-on-one meeting) is absolutely worth letting through.

My question was whether there's a policy suitably fine-grained to let me whitelist an app (or a certain type of notification) so that it can get around Do Not Disturb mode and reach me without having to completely shut down notifications from other apps in the settings.