Jakobodb

This utility plugin changes the theme of the current user to Sunrise, and uses the Sunrise color scheme when browsing the front-end, to help ensure you are viewing and editing the Development Site when making crucial changes to a site.
This plugin also adds a menu item to the admin bar to further confirm that you are on the Development Site.

Development Mode

Uses Sunrise theme on Dashboard and Frontend to visually represent development mode

Melissa Cabral

A simple, lightweight plugin that displays useful technical information on pages and posts to aid in developing WordPress Classic themes. Provides quick access to things that are sometimes hidden, like post/page ID, slug, taxonomy terms, and post type slug. Theme Inspector tells you exactly what conditional tags are true on each view, and what template file loaded on each page view.
<ul>
<li>Use In Conjunction with the <a href="https://docs.google.com/drawings/d/1hJ0MpHO3HKBT5KsTpGtc_gDYZ5pi-HyxNcRtmPBBULE" rel="nofollow ugc">WP Template Hierarchy Document</a>.</li>
<li>Theme Inspector is only visible to logged in Administrators.</li>
<li>Appears on the right-side of the Toolbar (admin bar).</li>
</ul>

Theme Inspector

A developer's inspector to illuminate the WordPress Template Hierarchy and help with building WordPress Classic themes.

Development Mode vs Theme Inspector