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.

GuyPrimavera

This open source and lightweight plugin allows users with the role Editor or Shop Manager to access the Menus and Widgets areas of the Appearance menu in WordPress’ admin area.
This is a common task that would be useful for clients to manage themselves to give them more control over their website’s content.
This plugin also gives access to the Customize submenu and other theme options, but these can be hidden through the options page at Appearance > Editor Access if you wish.
You can also select other menus to hide from Editors and Shop Managers (e.g. custom theme or plugin options pages), as well as hiding any elements on the Admin Bar.
Features
<ul>
<li>Allow access to Customize, Menus and Widgets for Editors and Shop Managers.</li>
<li>Theme Options remain hidden from these user roles.</li>
<li>Hide custom options pages from these users (if your theme/plugin has a custom settings page you wish to hide).</li>
<li>Hide any other menus or submenus. Simply select which menus you wish to hide.</li>
<li>Hide admin bar menus and elements. Choose which elements you wish to hide.</li>
</ul>

Editor Menu and Widget Access

Ideal

Allow and control Editor and Shop Manager access to the menus, widgets and appearance menu, plus other menus and adminbar items.

Editor Theme Options vs Editor Menu and Widget Access