Bastien Ho

NOUS Open Usefull &amp; Simple

This plugin is for you if :
<ul>
<li>You know CSS, but don’t have legitimacy to apply it</li>
<li>You manage a multisite network</li>
<li>You work with webmasters which want to customize WP but think that “CSS” means “Custom Super Style”</li>
<li>You just want to use predefined styles on your blog</li>
</ul>
This plugin works as well for standard single site or multisite network.
Checkout full examples and documentation on <a href="http://css-addons.avecnous.eu/" rel="nofollow ugc">css-addons.avecnous.eu</a>
The power user can create a set of CSS rules readable for humans with :
<ul>
<li>Slug</li>
<li>Name</li>
<li>Theme</li>
<li>Descrition</li>
<li>CSS code</li>
</ul>
It adds the list of addons in the customizer view (under appearance) and webmaster just have to check the ones they want with live preview. 
That’s it. 
For coder webmasters, a free field let them put there own CSS in a code-highlighted editor.
Predefined librairies are also available:
<ul>
<li>Bootstrap 3/4</li>
<li>GithubCSS</li>
<li>Knacss</li>
<li>MarkdownCSS</li>
<li>Normalize</li>
<li>Skeleton</li>
<li>YUI 3</li>
</ul>
<h3>Languages</h3>
<ul>
<li>en : 100%</li>
<li>fr_FR : 100%</li>
</ul>

Custom CSS Addons

Description: Lets administrator add CSS addons to any theme

Łukasz Nowicki

Post/Page/Product-specific custom code allows you to add custom CSS styles to individual posts, pages, or WooCommerce products. It provides a dedicated area in the editor screen where you can write your CSS code. You can also choose whether the CSS should apply only to the single view or also to archive-type views.
A new meta box will appear below the content editor on the edit screen for posts, pages, and products. You can enter any custom CSS there and decide whether it loads only on the single view or also on archive pages like category listings or product grids.
<h3>Requirements</h3>
This plugin requires at least WordPress 5.0 (remember always to keep your WordPress installation up to date!) and PHP 7.4 on your server.

Post/Page Specific Custom Code

Great plugin!

A very useful plugin

Add custom CSS to posts, pages, or WooCommerce products, with optional archive support. Includes a dedicated editor box.

Custom CSS Addons vs Post/Page Specific Custom Code