linewbie

WP Post Icon is a Free and Open Source WordPress plugin which is enable blog authors to upload and automatically insert topic icons or images in to your posts on the fly. You can control the position of the icon. Just select which image to display when you are writing a post, it will be automatically displayed.
<a href="http://www.linewbie.com/attach-diy/files/wp-post-icon.zip" rel="nofollow ugc">Download now!</a>
Features:
<ul>
<li>Automatically insert your topic icons in to your blog posts.</li>
<li>Very little manual work is required, just select which image to display when you are writing a new post.</li>
<li>
You could also use no image at all.
</li>
<li>
<a href="http://www.linewbie.com/sf-forum?forum=8&page=1" rel="nofollow ugc">Support</a>
</li>
<li><a href="http://www.linewbie.com/2008/02/wp-post-icon.html" rel="nofollow ugc">Version History</a></li>
<li><a href="https://wordpress.org/extend/plugins/wp-post-icon/faq/" rel="ugc">FAQ</a></li>
<li><a href="https://wordpress.org/extend/plugins/wp-post-icon/installation/" rel="ugc">Installation</a></li>
</ul>

WP Post Icon

Enables blogs authors to upload and select topic icons or images and have it automatically show up in their blog post.

Joris van Montfort

A plugin / toolset for anyone wanting to integrate (SVG) icons into the Gutenberg editor or options created with Advanced Custom Fields.
Add inline icons to rich text fields like: paragraphs, headings, lists or buttons anywhere in the WordPress block editor, or add a dedicated icon block from within the Gutenberg editor.
This plugin ships with the free Font Awesome icon set as default icon set. You can choose between version 4.x, 5.x and version 6.x. 
The dedicated icon block contains several styling options to customize the icon in the icon block. 
The plugin also provides an easy to use interface for creating a custom icon set based on SVG icons. Custom icons can be uploaded from the plugin settings using an easy to use drag & drop uploader.
For users of Advanced Custom Fields (ACF) the plugin also creates a new field type: JVM Icon. This allows you to create custom fields that work with a the font awsome icon or any custom created icon set.
If font awesome or the built in custom icon set configurator do not meet your needs you can also create your own custom icon set and load it using hooks provided by the plugin.
The plugin simply inserts icons in the following HTML format:
<pre><code> 
</code></pre>
The CSS class names and available icons can be all be modified to your liking if you are prepared to write some PHP hooks for your WordPress theme. Please note that you should keep the plugin settings set to use ‘Font Awesome 4.7’. 
If you would like to load a custom created webfont or icon set you crafted yourself please read on. If you have the SVG files you can set the plugin settings to ‘Custom SVG icon set’ and upload your SVG files from the plugin settings.
CSS file 
A slightly customized version of the Font Awesome 4.7 CSS file is loaded by default on the front end and backend to make the plugin work out of the box, but you can also choose Font Awesome Free version 5.x or 6.x from the settings screen. 
If you want to use a custom created icon set it is advised to overide the icon set json file and CSS file using hooks provided by this plugin.
Custom icon set file 
If the plugin is set to Font Awesome 4.7 icon set (default behaviour) the icons are loaded from: wp-content/plugins/jvm-richtext-insert-icons/dist/fa-4.7/icons.json. The json file contains all css classes that can be turned into icons by Font Awesome 4.7 CSS file. You can load a custom json icon set file by calling a filter hook in your (child) theme functions.php. 
For example:
<pre><code>function add_my_icons($file) {
 $file = get_stylesheet_directory().'/path_to_my/icons.json';
 return $file;
}

add_filter( 'jvm_richtext_icons_iconset_file', 'add_my_icons');
</code></pre>
The icon config file can also be in fontello format since version 1.0.3. Have a look at: <a href="https://fontello.com" rel="nofollow ugc">https://fontello.com</a> to create your customized icon set.
Custom CSS file 
By default the Font Awesome 4.7 CSS is loaded from: wp-content/plugins/jvm-richtext-insert-icons/dist/fa-4.7/font-awesome.min.css. You can load a custom CSS file for your icon set by calling a filter hook in your (child) theme functions.php. 
For example:
<pre><code>function add_my_css($cssfile) {
 $cssfile = get_stylesheet_directory_uri().'/path_to_my/cssfile.css';
 return $cssfile;
}

add_filter( 'jvm_richtext_icons_css_file', 'add_my_css');
</code></pre>
If you choose the load your own CSS file and want to disable the default CSS file use the following code:
<pre><code>add_filter( 'jvm_richtext_icons_css_file', '__return_false');
</code></pre>
All icon markup has the classname “icon” prefixed to the icon HTML inserted. If you want to use some other prefix you can add a filter. Like this:
<pre><code>function my_icon_class($css_class_name) {
 return 'my-custom-css-class-name';
}

add_filter( 'jvm_richtext_icons_base_class', 'my_icon_class');
</code></pre>
Use this hook to disable the entire plugin settings screen that was added in 1.0.9:
<pre><code>add_filter('jvm_richtext_icons_show_settings', '__return_false');
</code></pre>
Please note that settings will still be loaded so please make sure you have set the settings to default font awesome if you are loading a custom icon set with the plugin hooks.

JVM Gutenberg Rich Text Icons

Thank you so much for the plugin, Joris! I am using a modded version of this plugin to insert a custom icon pack that I created. It was so easy to configure.

You have my utmost respect for this amazing plugin.

Incredible and Highly Extensible

Even though the plugin could not be activated due to a syntax error (which I fixed it - to be more accurate - bypassed it), it eliminates the need for me to create a similar block with ACF Pro for my projects, so thank you for this plugin.

Does one job, and does it well.

I can imagine something like this becoming part of core. Very well developed essential addon for the block editor

great gutenberg addon

Add Font Awesome icons, or icons from a custom icon set to rich text fields anywhere in the Gutenberg block editor!

WP Post Icon vs JVM Gutenberg Rich Text Icons