WordFez is a plugin for bilingual (French-English) posts. It is seamlessly integrated into WordPress using a TinyMCE plugin.
It will add 2 extra buttons in the WYSIWYG interface for French and English language. Each button inserts 2 anchors to surround each language. The anchors are labeled by small flags. 
The usage is very straight-forward. The plugin comes with a widget to allow each reader to conveniently and instantly switch between the languages.
You need WordPress 2.5 at least.
New in v0.2.1:
<ul>
<li>Compatibility with WordPress 2.5</li>
<li>Fix a small problem in ‘alt’ fields</li>
</ul>

WordFez

WordFez is a plugin for bilingual (French-English) posts. It is seamlessly integrated into Wordpress using a TinyMCE plugin.

WordPress.org

iseulde

This plugin adds the following functionality:
<ul>
<li>Code <code>code</code>, subscript <code>sub</code>, and superscript <code>sup</code> buttons to the formatting toolbar.</li>
<li>Inline text and background colour panel (found inside the block sidebar for now).</li>
<li>Remove formatting button (found inside the block sidebar for now).</li>
</ul>

Advanced Rich Text Tools for Gutenberg

Great plugin.  Now I just need to find a quick way to change the font style

Thank you so much!

No more need to use the HTML view to insert Code. Thanks a lot. Exactly what I was looking for. It just works!

A real work relief

Additional tools for rich text fields in Gutenberg.

WordFez vs Advanced Rich Text Tools for Gutenberg