Jake Bresnehan

This plugin provides you an easy quick way to test your content looks good at various sizes.
Features of the plugin include:
<ul>
<li>Mobile view</li>
<li>Tablet view</li>
</ul>
Getting setup with the plugin
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/bXe5_BvvtxA?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
<a href="http://web-design-weekly.com/support/" rel="nofollow ugc">Plugin Support & Feature requests</a>.

Responsive Post Preview

Adds the ability to view your posts and pages at different viewport sizes with a click of a button

keesiemeijer

Add additional content on a post per post basis in the edit or publish post screen. The additional content editor can be used with all public post types.
Use this plugin for content that you, for whatever reason, don’t want to be included in the post content itself, like <a href="https://keesiemeijer.wordpress.com/2015/05/25/how-to-remove-specific-shortcodes-from-post-content/" rel="nofollow ugc">shortcodes</a>, or code snippets used by other plugins.
Another benefit of using this plugin is if you want content to be displayed before or after content that is automatically added by other plugins. The <a href="https://wordpress.org/plugins/additional-content/faq/" rel="ugc">priority parameter</a> will let you do just that.
For more information visit the <a href="https://github.com/keesiemeijer/additional-content" rel="nofollow ugc">GitHub repository</a>.

Additional Content

Display additional content before or after post content in single post pages.

Responsive Post Preview vs Additional Content