Unlike other OEMs, Samsung has notification silencing options, but the terminology is different. Instead of priority mode, you’ve got Do Not Disturb (DND). You can access these settings by going to the main system settings, then Device > Sound notifications > Do not disturb. You can turn on DND from here or with the notification toggle. Still, you’ll also want to look at the scheduling options to have DND flip on automatically. Lastly, add exceptions to Do Not Disturb. So your most important contacts can still get through while the phone is silenced.
Customize Notification Shade Toggles