Samsung
Mute a Conversation in Messages auf Samsung
Samsung Messages treats notification settings per conversation, not just per app. That means you can turn off alerts for one specific chat while every other conversation keeps notifying you normally.
To do this, open Messages ➔ Tap and hold a Conversation ➔ Tap on Notifications. From there you can switch the notification toggle off for that thread. The change applies only to that contact or group, not to your entire Messages app.
Muting is not the same as blocking. A muted conversation still receives new messages and they still appear in your inbox, but your phone stays silent and the screen does not light up for them. Blocking, by comparison, prevents the messages from reaching you at all.
This is useful for group chats with constant activity or a contact who sends frequent updates you do not need to see immediately. It is less useful if you occasionally expect an urgent message from that same contact, since you will not get an alert even for something time-sensitive.
To bring notifications back, repeat the same steps and switch the toggle back on. The setting is stored per conversation, so it stays muted until you change it again yourself.