Markdown Editor, is an editor for markdown language (a lite markup language with plain text formatting syntax).
There are few settings to adjust for this app, simply open any markdown document, edit the code on the left side editor, then adjust desired options on the top toolbar, and then click on the compile button. Please note that the add-on also compiles the code on-the-fly as you type in the editor. Once you are done, you can download the final markdown code or get the PDF for the final result.
If you have a feature in mind or found a bug to report, please fill the bug report form in the add-on's homepage (https://mybrowseraddon.com/markdown-editor.html).