CryoutCreations

Quickly and easily swap between themes. Adds a theme switcher to the WordPress Admin Bar with all parent/child themes, filtering and favorites list. Compatible with WordPress 4+ 
Performs transparent theme switch by redirecting to the initial URL on both the frontend and in the dashboard.

Cryout Theme Switch

Quickly and easily swap between themes. Adds a theme switcher to the WordPress Admin Bar with all parent/child themes, filtering and favorites list.

sevenspark

The Menu Swapper provides two utilities:
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A settings page that allows you to register unlimited menu theme locations
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A meta box that will appear on Pages and Posts, which will allow you to replace existing menu theme locations with your new theme locations for those individual Posts/Pages.
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<a href="http://www.youtube.com/watch?v=kAd0_RKvvLw" rel="nofollow ugc">Video demo</a>

Menu Swapper

The Menu Swapper allows you to register custom theme locations and easily swap menus on individual Pages or Posts.

Cryout Theme Switch vs Menu Swapper