Jonathan Bardo

Note: This plugin only works with WordPress 4.2 or higher
This plugin will enable the site administrator to easily create an admin message present on all pages. The admin has the option to let the user dismiss the message for the duration of his session.

Admin User Message

This does just what I want. Thanks for making it. :)
It's definitely better than https://wordpress.org/plugins/admin-screen-messages
You might want to also tag it as:
https://wordpress.org/plugins/tags/admin-message



Perfect

Add message to users of your site. Choose wheter they can dismiss it or not.

wp.insider

smp7

This addon allows you to customize the content protection message that gets output from the membership plugin.
You will be able to specify your custom messages for different types of protection message.
This addon requires the <a href="https://wordpress.org/plugins/simple-membership/" rel="ugc">Simple Membership Plugin</a>.
After you install this addon, go to the “Custom Message” menu from the admin dashboard to use it.
Read <a href="https://simple-membership-plugin.com/simple-membership-custom-messages-addon/" rel="nofollow ugc">Usage Documentation</a>

Simple Membership Custom Messages

Simple Membership Addon to customize various content protection messages.

Admin User Message vs Simple Membership Custom Messages