Cliff Seal

Simply put: this plugin gives the Editor role access to edit “theme options”, which includes:
<ul>
<li>Appearance > Widgets</li>
<li>Appearance > Menus</li>
<li>Appearance > Customize if they are supported by the current theme</li>
<li>Appearance > Background</li>
<li>Appearance > Header</li>
</ul>
Instead of adding this capability by hand on each client site, just install and activate this plugin—it keeps your <code>functions.php</code> file clean, and keeps this type of functionality where it belongs.
The capability is added to the role once (on plugin activation) and removed when the plugin is deactivated.

Editor Theme Options

Allow editors to access theme options in the Appearance menu.

Kris C

Add Customizer plugin adds the customize option back to the admin appearance menu.
<h3>How</h3>
Using this plugin:
<ol>
<li>Install the plugin.</li>
<li>Activate the plugin.</li>
<li>Navigate to the dashboard -> appearance menu.</li>
<li>Click on the customizer link.</li>
</ol>

Add Customizer

This little plugin has clean code and does one thing really well. Great job!

Very useful

Adds the customizer link in the admin appearance menu.

Editor Theme Options vs Add Customizer