Markie is a wysiwyg editor for the markdown syntax written entirely in python with html preview of your own css.Discontinued
Last Update: 31.01.2008, see https://codeboje.de/wysiwyg-markdown-editor/
MDYNA is a rich Markdown note taking app capable of syncing with GitHub Gist for easy cloud-based note management. The app is made with Electron and is open-source and cross-platform.
MarkdownNote makes it really easy to create notes using John Gruber’s popular Markdown markup language in your iPad. Using live preview feature, you can preview your Markdown markup syntax to HTML on writing.