[jakswa]

I still have my pitchfork from all the bugs I encountered when they released the new formatting (still works wonky depending on the workspace for me). That said, I believe this is an option since they changed things:

  I have yet to hear a good argument for not having a little button to enable raw Markdown mode.

That toggle is buried in the preferences/settings under "advanced."

  Format messages with markup
  The text formatting toolbar won’t show in the composer.