crimson090

Adds buttons to the Text (HTML) edit which generate Markdown syntax. These buttons serve as a great introduction to 
users who are new to Markdown, as well as shortcuts for more experienced users. The buttons include:
<ul>
<li>Bold</li>
<li>Italic</li>
<li>Blockquote</li>
<li>Link</li>
<li>Code</li>
<li>Table</li>
<li>Headers</li>
<li>Help (links to external Github Markdown guide)</li>
</ul>
This plugin does not modify the Visual editor, as that editor is not ideal for writing Markdown in. It’s recommended you disable 
the Visual editor entirely to enforce using Markdown.
Note that this plugin does not render Markdown. You should use a plugin (such as Jetpack Markdown) to render markdown in your theme.

MarkdownBar

Adds a toolbar of buttons to the Text (HTML) edit which generate Markdown syntax

Steve Grunwell

<a href="https://codex.wordpress.org/Excerpt" rel="nofollow ugc">WordPress post excerpts</a> can be a great way to hand-craft the summary of your content. Unfortunately, writing post excerpts isn’t as nice of an experience as what you find elsewhere in WordPress. Want to include links in your excerpts, or bold some text? Hopefully you know some HTML!
Advanced Post Excerpts is designed to change that, by giving your editors an easy, intuitive interface for writing great post excerpts.
For complete details and/or to contribute to ongoing development, please <a href="https://github.com/stevegrunwell/advanced-post-excerpt" rel="nofollow ugc">visit this project on GitHub</a>.

Advanced Post Excerpt

Replace the default Post Excerpt meta box with a superior editing experience.

MarkdownBar vs Advanced Post Excerpt