bmsterling

This plugin adds more buttons to the non-visual editor view for creating/editing posts/pages
Currently adds: 
* h1 
* h2 
* h3 
* h4 
* h5 
* q 
* cite 
* sub 
* sup 
* dl 
* dt 
* dd
<h3>Credits</h3>
Copyright 2012 Benjamin Sterling (benjamin.sterling@kenzomedia.com)
This program is free software; you can redistribute it and/or modify 
it under the terms of the GNU General Public License, version 2, as 
published by the Free Software Foundation.
This program is distributed in the hope that it will be useful, 
but WITHOUT ANY WARRANTY; without even the implied warranty of 
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
GNU General Public License for more details.
You should have received a copy of the GNU General Public License 
along with this program; if not, write to the Free Software 
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

Quicktag Extender

This plugin adds more buttons to the non-visual editor view for creating/editing posts/pages

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.

Quicktag Extender vs Quicktags for WP