WordPress post metadata plugins

PureDevs Any Meta Inspector shows all the meta keys and their unserialized values in a metabox for posts, pages, terms, comments, and users.

Manage and edit post meta data directly from the post edit screen — view, add, update, or delete meta fields instantly using AJAX without page reload.

SatishDB Cleaner — Remove Revisions & Dummy Content (posts, pages, and custom post types).