There are two things that cb could do for you:
1. provide syntax highlight
2. allow you to run a tool that renders the text in markdown.
I'm not sure if 1 is possible, someone should inspect the scintilla's docs if it has a markdown lexer.
Two is already possible with Tools or Tools+, you just need to find a markdown renderer.
Anything else is outside of the scope of an IDE - a tool for writing code, not formatted text documents!