Brian Alexander

Adds the current page’s template name to the admin bar.
Because this plugin reveals potentially sensitive information about the active theme, it is recommended for development environments only, and should not be enabled on a production site.

What Template

Adds the current page's template name to the admin bar.

Matt Cohen

Matty Theme QuickSwitch makes it easy to activate a theme without needing to visit the “Appearance -> Themes” screen in the WordPress admin.
A new menu in the WordPress Toolbar lists all themes currently available on your website, with quick links to activate each individually.
Theme QuickSwitch is particularly useful when developing or debugging WordPress themes, as it saves time in getting you to the place you need to be.

Matty Theme QuickSwitch

Quickly switch between themes via a menu in the WordPress Toolbar.

What Template vs Matty Theme QuickSwitch