wpler

<a href="https://www.wpler.com/linkmanager-fur-multisites/" rel="nofollow ugc">Deutsche Beschreibung des Plugins</a>
You run a Multisite Blogsystem with open registration for users to add own blogs and their can using a theme by 
different installed themes, but you want to show a link into the footers of the themes but only once time and for 
every blog another one?
With this plugin you can manage your outgoing links into the themes by a shortcode/function for every blog. You can 
set for every link the target, relation (Attribute rel), linktext and -title and the target url. Also you can set more 
than one link for a blog.
For output you can use a shortcode or a function . This function get the links 
for the current blog-id and printed this, if links are available.
All options/links can set by network admin only. The outputs needs no capability.

WPMU LinkManager

Manage your Themes footer links for every blog into a multisite includes with conditional tags.

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.

WPMU LinkManager vs Insert Headers And Footers