View Single Post
When I downloaded it and unzipped it the resultant folder's name was actually:

"fletcher-Markdown.ooxsl-820ace92d65af96573e97250331c5c4d36aece39"

which I just moved as is to the folder indicated. I couldn't get it to work until I renamed the folder to just "fletcher-Markdown.ooxsl" - at which point it began to appear as a single file in the finder. After a restart of Omni Outliner, I began to see the markdown options appear in the export menu as a save option.

Hope that helps.