Igor Benic

This is a plugin that will enable you to add alerts, info and similar chunks of text.
This is useful when creating tutorials and you want the reader to be notified of a change in code or something to check. Info blocks are used in technical Books when you want to point some information or you want the reader to read a part that is important to understand the next piece of code.
This is also suitable when you republish articles on your blog to inform the user on what has changed.
Info Blocks also allow you to change:
<ul>
<li>Background color</li>
<li>Text color</li>
<li>Padding (size and unit)</li>
<li>Dashicon Icon (or leave it off)</li>
<li>Icon Size</li>
<li>Space between the Icon and Text</li>
</ul>

Info Blocks

A gutenberg block for creating alerts, information or update text

Remi Corson

This plugin helps admins to easily create admin notification inside the WordPress administration.
You can choose many options and decide how and where to display the notifications.

Easy Admin Notification

Tested up to 3.3.1 Stable Tag: 1.4 Adds the ability to create easily notification in the admin panel

Info Blocks vs Easy Admin Notification