Actually, Apple Shortcuts will do this quite nicely, especially as of this fix:
Then, if you take something like this shortcut (warning: this will break your outline), you can convert an outline like this:
into markdown that looks like this:
# A heading
Some **rich** _italic_ text with a [link](https://www.example.com)
# Another heading
Some more **rich** text with highlight (won’t translate to markdown)
And strikethru (also won’t translate to markdown)
> A quote
*A note*
## Second level heading
- [ ] A task
- [x] A done task
Some more stuff here
### More headings
* Lorem ipsum dolor sit amet.
#### Even
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
##### More
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
###### Headings
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
# Yet another heading
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et **dolore** _magna_ aliqua.