tljorgensen

Simple Post Inserter takes various inputs through the settings page and determines three things:
The content you wish to display in your posts, could be plain text, could be some HTML code. 
By default the admin of the site is responsible for any of the content submitted.
The location where the content should be displayed within the post.
Post restrictions. By default if no other setting but the content and location are declared, 
the plugin will insert the content in all of the posts available on the site. This may not be what you 
desire, but you can filter by post type, category, and ID.
Currently the only parameter for placement inside the posts is based off of total paragraphs in a post. 
This will likely change in a future update to something a little more sensible such as: lines of text or character counts.

Simple Post Inserter

Simple post inserter does what it sounds like. Insert some content into a post at your desired location.

LuckyWP

The “LuckyWP Scripts Control” plugin allows you to insert and manage custom code into website. For example, you can insert Google Analytics code, Google Search Console verification meta tag, Facebook pixel, custom CSS/JS and other code without edit theme files.
<h4>Features</h4>
<ul>
<li>Great user interface: simple and functionally.</li>
<li>Insert code before <code></head></code>, after <code><body></code> or before <code></body></code>.</li>
<li>Items sortable.</li>
<li>Add Google Analytics code.</li>
<li>Add Google Verification meta tag.</li>
<li>Add Google Tag Manager code.</li>
<li>Add Facebook pixel code.</li>
<li>Add custom meta tags.</li>
<li>Add custom JS/CSS/HTML code.</li>
<li>RTL support.</li>
</ul>

LuckyWP Scripts Control

A great way to insert and manage custom code (CSS, JS, meta tags, etc.) into website before </head>, after <body> or before </body>.

Simple Post Inserter vs LuckyWP Scripts Control