Theme Junkie

This plugin will enable a <a href="https://www.theme-junkie.com/plugins/theme-junkie-custom-css/" rel="nofollow ugc">custom css manager</a> on administration page to add Custom CSS code to your WordPress website. It will automatically override any theme or plugin default styles. It also very useful if you want to add customization to your website but do not want to edit your theme or plugin css files.
It comes with two ways to add the custom css code:
1. Setting 
You can go to Appearance → Custom CSS, then you will see a big box/textarea. Put your css code there.
2. Customizer – Live Preview 
If you want to see the live preview while you adding the custom css code, then you can go to Appearance → Customize, after that open the Custom CSS section tab.
<h4>Features Include:</h4>
<ul>
<li>No configuration needed</li>
<li>Live preview</li>
<li>Easy-to-use</li>
<li>Child theme alternative to add customization</li>
<li>Uninstall procedure</li>
</ul>
<h4>Plugin Info</h4>
<ul>
<li>Developed by <a href="https://www.theme-junkie.com/?utm_source=wporg&utm_medium=text_link&utm_campaign=Site%20Promotion" rel="nofollow ugc">Theme Junkie</a></li>
<li>Check out the <a href="https://github.com/themejunkie/theme-junkie-custom-css" rel="nofollow ugc">Github</a> repo to contribute.</li>
</ul>

TJ Custom CSS

Simply works

Easily to add any Custom CSS code to your WordPress website.

Adnan

WPBrigade

Muhammad Irfan

WP Headers and Footers plugin helps you to insert code to your WordPress website headers and footers section like Google Analytics tracking code, Facebook Pixels code, Google Optimize code for A/B testing, Custom CSS code, and more. You don’t need to edit the theme files to insert the code.
The simple interface of this plugin allows you to add code and different scripts from one place to your WordPress website (Headers, Footers, and Body section).
Features
<ul>
<li>Insert code to your WordPress headers & Footers</li>
<li>Insert Google Analytics Code to any WordPress theme</li>
<li>Insert Facebook Pixels Code</li>
<li>Add Google Optimize Code for A/B testing ( Ab Testing )</li>
<li>Add Google search console authentication code to any theme for verification</li>
<li>Add Custom CSS, any script, and HTML to your website 
Google Tag Manager code/script insertion</li>
<li>You can also insert code to your website body section 
Can add Bing webmaster tool code for website verification 
Add Google AdSense code</li>
</ul>
If you find our plugin useful, please leave a good rating/review and check our other plugins.
<ul>
<li><a href="https://analytify.io/ref/73/?utm_source=wp-headers-and-footers&utm_medium=readme&utm_campaign=pro-upgrade" rel="nofollow ugc">Analytify – Google Analytics Plugin</a></li>
<li><a href="https://loginpress.pro/" rel="nofollow ugc">LoginPress</a> – For Custom login page and login page security</li>
<li><a href="https://simplesocialbuttons.com?utm_source=wp-headers-and-footers&utm_medium=readme&utm_campaign=pro-upgrade" rel="nofollow ugc">Simple Social Buttons</a> – Plugin for Social share buttons and social icons</li>
<li><a href="https://wordpress.org/plugins/related-posts-thumbnails/">Related Posts Thumbnails Plugin</a> – For related posts/products</li>
<li><a href="http://wpbrigade.com/recommend/maintenance-mode?utm_source=wp-headers-and-footers&utm_medium=readme&utm_campaign=pro-upgrade" rel="nofollow ugc">Under Construction, Coming Soon & Maintenance Mode</a> – Plugin for Under construction & Coming soon page</li>
</ul>

Insert Headers And Footers

I like its simple design which doesn't add menu item on top level of WP admin menu. Recommended for client works and who prefer to keep WP admin menu simple. I hope you continue its simple style than adding functionalities.

Simple UI

Include inline javascript, stylesheets, CSS code or anything you want in Header and Footer areas of your WordPress with ease.

TJ Custom CSS vs Insert Headers And Footers