Ryan

Adds a section to the bottom of your pages and posts listing any external 
links.
Only links starting with http or https are included so ftp, mailto, etc 
will not be included in the list; although it would be pretty trival to 
edit the plugin to allow them to. Likewise any links that start with your 
blog URL are also excluded.
For more information, you can visit <a href="http://www.nutt.net/tag/link-footnotes/" rel="nofollow ugc">Nutt.net</a>

Link Footnotes

Adds a footnotes section to your posts with any external links

Corrado Franco

This plugin allows one to create footnotes by using markdown notation. 
It is for footnotes only. No other markdown tag is taken into account
Example:
<pre><code>I have more [^1] to say up here.

[^1]: To say down here.
</code></pre>
If used with jetpack and enabled markdown, it only shows the buttons without modifying the text content. 
Unlike jetpack-markdown, footnotes will appear in the exact point where they have been inserted. To go back to text mode click on the footnote number.
N.B 
This plugin also works with Gutenberg. But the button only appears in the Classic Editor. 
For now with Gutenberg enter the codes directly.
<h3>Configuration</h3>
No configuration is necessary.
Considering that this plugin, like others working with “markdown”, parsing the page every time I load it, I highly recommend using a caching plugin.

Blank Footnotes

Simple plugin to show footnotes using markdown notation.

Link Footnotes vs Blank Footnotes