Philip Newcomer

This plugin makes all custom fields (post meta) visible in the “Custom Fields” meta box on post edit screens.

Show Hidden Post Meta

As a plugin developer, I create hidden post meta all the time and sometimes I need to see it to debug it. This does what it says it does, and well. Its simple and hasn't been updated for a while, but I'm glad it exists!

PS: If you need someone to take this one over, let me know. I'll keep it tested and updated if you're unable to.

Still works on 5.5

Makes hidden post meta visible on post edit screens

Automattic

Daniel Bachhuber

A quick and easy way to see post meta associated with any given post. When activated, this plugin prints your post meta keys and values inside of a post meta box.
Originally developed for <a href="http://vip.wordpress.com/" rel="nofollow ugc">WordPress.com VIP</a>-hosted clients, we thought it would be useful for development environments, etc. too. Feel free to <a href="https://github.com/Automattic/Post-Meta-Inspector" rel="nofollow ugc">fork the plugin in Github</a> and pull requests are always welcome. Hit us with feedback, questions, bug reports, and feature requests in the forums.

Post Meta Inspector

Lovely little tool. Saves having to go into the database and look through the postmeta table when debugging. Thanks!

Show Hidden Post Meta vs Post Meta Inspector