Recs.
Updated
Zettlr is a Markdown editor that focuses on all the things one needs to write texts. It offers inline previews, citeproc support, easy exporting to all formats (even slideshows), syntax highlighting for many languages, and is cross-platform.
SpecsUpdate
Pros
Pro Focuses on writers
While many Markdown editors don't offer specific support for a certain type of workflow, or offer features for scientific workflows only, Zettlr offers features that help the writing process of journalists or researchers in the arts and humanities. It's a lot more text-focused than most editors.
Pro Almost perfect
This is the best option, still not perfect, there are some bugs like creating / editing tables and resizing images, but the PROS destroy the CONS, easy quotes, WYSIWYM , attachments tab (supports attaching and opening links to any file), table of contents, TAGs, easy hyperlink between files (same as citations), export to many formats (like Word, HTML5, PDF)...