I’m trying to figure out whether an Action is possible on the Mac that I have set up already with Drafts and Shortcuts on my iPhone, preferably without spending hours learning JavaScript.
The Action on my phone creates a PDF from the Draft and then attaches it to an email, with the To: field pre-filled based on what I choose from a Menu in Shortcuts (I choose a client’s name and it fills in the To: field with the corresponding support personnel that need to receive the report).
Programmatic generation of a PDF from Markdown on the Mac, - try Pandoc.
Drafts can also run AppleScript to control other applications, so maybe send an e-mail via the Apple Mail app, with a file attachment using AppleScript; the attachment being the PDF generated via Pandoc.