Admin -> Message Styles is the library of reusable alert content templates. Each Style has a Subject/Body Template with MA:xxx tokens filled in when an alert fires -- completely independent of which Channel it goes through. A live preview renders your template against sample data as you type, with a destination picker showing exactly how each platform's markup dialect will (or won't) render it.

See the full Alerting guide for the token reference and the cross-platform formatting table (Teams/Slack/Discord/Google Chat/email all handle bold, italics, and links differently).