Yup this! Set a channel (whatever you want to call it i.e. emergency). Then once you get the notification on your device, long hold on the notification until you get the settings cog. Tap that. You will then get a list of all notification channels for that specific app. Find the one you selected for this channel and tap it. You then get to select the notification settings for that specific channel. You can set if it pops, the sound, vibration etc. Would recommend the override do not disturb setting for something like this.
Do not disturb on MIUI 12; exclusions
Can someone with MIUI 12 check something for me? Is it possible to create exclusions while in the do not disturb mode? So in settings -> apps, select a random app, click notifications. There should be some sort of ignore DND option, hopefully...