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

Andrew Ozz

This plugin is intended for more advanced users that would like to change the default TinyMCE configuration in WordPress. 
It makes it very easy to add, remove or change all TinyMCE settings for the classic editor and for the classic block in the block editor.

Advanced TinyMCE Configuration

Set advanced TinyMCE options for the classic block and classic editor.

MarkdownBar vs Advanced TinyMCE Configuration