I wrote a single-javascript-step action to take selected text in CSV format and convert it to a Markdown table. The Markdown overwrites the selected text.
When you run the action it allows you to specify whether the first row is to be treated as a heading row or not.
It makes no attempt to parse whether a column should be left-, right-, or centre-aligned. You can easily adjust these yourself after you run the action.
The action is shared here: https://actions.getdrafts.com/a/1Qk
I’ve only tested it with Drafts 5.