Vitalii

This plugin can to quickly switch user by click. It is comfortable for develop themes and plugins.
After load page, loading neat closed sidebar from right. By click on arrow it show or hide sidebar. Sidebar is 
displaying all registered WordPress users. By click on user is ajax send user ID to back end where switch user. 
After response is JavaScript reload page with registered new user.
<h3>Why using iBryl Switch User?</h3>
<ol>
<li>Quickly switches user by click.</li>
<li>Doesn’t slow down loading.</li>
</ol>

Plugin Name: iBryl Switch User

This plugin can to quickly switch user by click. It is comfortable for develop themes and plugins.

3D Virge

With this plugin you can switch the different WordPress notification e-mails on and off, like options as the new user and password change notifications send by WordPress to the administrator and user. Works perfectly in combination with a lot of other plugins!
Watch this nice tut made by Robert Orzanna: 
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/66UkQKgSFio?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>
The options you can manage are:
<ol>
<li>New user notification to admin</li>
<li>New user notification to user</li>
<li>Notify post author</li>
<li>Notify moderator</li>
<li>Password change notification to admin</li>
<li>Password change notification to user</li>
<li>E-mail address change notification to user</li>
<li>Forgotten password e-mail to user</li>
<li>Forgotten password e-mail to administrator</li>
<li>Automatic WordPress core update e-mail</li>
<li>Automatic WordPress plugin update e-mail</li>
<li>Automatic WordPress theme update e-mail</li>
<li>Send admin notifications to extra admin e-mail addresses (1.7.0)</li>
<li>Send an e-mail to administrators after a user requested to update his or her e-mail address (1.7.0)</li>
<li>Send an e-mail to administrators after a user successfully updated his or her e-mail address (1.7.0)</li>
<li>Multi-site support! Now you can manage your notification settings in one single environment (1.8.0)</li>
<li>Export and import settings (1.8.0)</li>
</ol>
The automatic core, plugin, and theme updates have a special built-in feature. When one of these options is disabled, successful e-mails don’t get send out, but failed updates still will send an e-mail to the admin.
This version contains some nice new stuff. If you find any issues, let me know. If you like the new features, please be so kind to give this plugin a good rating! It will help me to keep up the good work for you 🙂
Want regular updates? Feel free to support me with a small donation 🙂

Manage Notification E-mails

Enable and disable email notifications that WordPress sends to the admin and user. Works perfectly with many other plugins!

Plugin Name: iBryl Switch User vs Manage Notification E-mails