I use Typora free (commercial license, not open source) markdown editor for Windows/Mac/Linux because it works very fast. The latest version of Typora is currently a beta version and it's free software, but Typora may cost something in the future.
Typora can capture rich content directly from word processors and webpages, convert it directly into markdown text via copy/paste, and it preserves the original formatting too. Typora can capture in this way formatted lists, headings, formatted text, hyperlinks, and images.
Typora will give you a seamless experience as both a reader and a writer. It removes the preview window, mode switcher, syntax symbols of markdown source code, and all other unnecessary distractions, and replaces them with a real live preview feature to help you concentrate on the content itself.
editiing a table in live preview mode
Mark Text free markdown editor for Windows/Mac/Linux is better than Typora at accurately capturing everything on a webpage and Typora has a more user-friendly editor, so I use both applications. I use Mark Text as a webpage grabber, and then I copy/paste the markdown text I captured into Typora and use Typora to edit it.