OnePlus
Silence Notifications From Individual Apps auf OnePlus
Muting a single app on your OnePlus phone leaves its notifications sitting in the shade and on the lock screen, but strips out the sound, vibration and pop-up banner. That is the setting you want when an app like WhatsApp keeps buzzing constantly, but you still want to catch up on messages later without losing them.
OxygenOS controls this per notification category, not just per app. A messaging app usually splits its alerts into categories such as messages, group messages or calls, so you can mute only the noisy category while leaving others active.
To reach the setting: Open the Settings ➔ Tap on Apps & notifications ➔ Tap on See all apps ➔ Choose an app ➔ Tap on Notifications ➔ Choose a category ➔ Enable Other. Turning on Other inside a category removes sound and vibration for that category while the notification still appears in the shade.
This differs from turning notifications off entirely for an app, which removes them from the shade and lock screen as well. If you only need quiet hours instead of permanent muting, a scheduled Do Not Disturb mode fits better than muting each app one by one.

