MWeb can handle professional-level markdown with support for markdown extensions. It provides publishing to various social networks and blogging formats, as well as various preview themes. It also has two work modes: external, which allows the addition of external folders; and library, designed for note-taking and static blogging.
Full GFM (GitHub Flavored Markdown) supported
Publish/Update to WordPress, Metaweblog API services, WordPress.com, Evernote, Blogger, Tumblr.
Drag-and-drop or paste to insert pictrue and display immediately.
Live preview and export to PDF/HTML/RTF/DOCX
External folder, library, static blog/website generator
OS X 10.9 or later, 64-bit processor