Tom McFarlin

Excerpt Check prompts authors to add an excerpt before publishing or scheduling a post. When no excerpt is present, a modal appears giving the author the choice to add one or proceed without it. This works seamlessly in both the Classic Editor and the Block Editor (Gutenberg).
Features:
<ul>
<li>Intercepts publish and schedule actions when no excerpt is present</li>
<li>Full support for the Classic Editor and the Block Editor (Gutenberg)</li>
<li>Modal prompt that surfaces before the post is saved</li>
<li>Two configurable modes: Remind (allow publishing anyway) or Require (must add an excerpt)</li>
<li>Settings integrated into the existing Settings > Writing page</li>
<li>Works with any post type that has excerpt support enabled</li>
<li>Lightweight with zero impact on front-end performance</li>
</ul>
Why use excerpts?
WordPress can auto-generate excerpts by truncating post content, but the results are often incomplete sentences, leftover shortcodes, or broken HTML. Custom excerpts give you full control over how your posts appear in archive pages, search results, RSS feeds, and SEO meta descriptions.
Use Cases:
<ul>
<li>Content teams that enforce editorial standards requiring excerpts on all posts</li>
<li>SEO-focused publishers who rely on custom excerpts for meta descriptions</li>
<li>Multi-author blogs where editors want to ensure consistent content quality</li>
<li>Any site where auto-generated excerpts are not desirable</li>
</ul>

Excerpt Check

Prompts authors to add an excerpt before publishing or scheduling a WordPress post. Plugin Homepage

David Klhufek

This simple plugin adds useful buttons to the native WordPress HTML editor (Classic Editor).
Currently adds: 
h1, h2, h3, h4, h5, span, hr, nbsp, mox
The “mox” button adds a nice responsive CSS class which you can use to highlight pictures or other elements in your posts.
Note: This plugin works only with the Classic Editor. It does not support the new Gutenberg (Block Editor).
<h3>Compatibility</h3>
<ul>
<li>Requires the Classic Editor to be active. </li>
<li>Designed specifically for the HTML mode of the editor.</li>
</ul>

Quicktags for WP

This simple plugin adds useful buttons to the native WordPress HTML editor.

Excerpt Check vs Quicktags for WP