Rewrite Rules Viewer and URL Tester
Adds Tools > Rewrite Rules, listing every rewrite rule and showing which rule and query a URL path you enter would match, for debugging 404s and custom permalinks.
Snippet Library
Developer snippets for WordPress
Snippets for developers: debugging helpers, custom cron schedules, body classes, REST API tweaks and admin tools for checking hooks and queries. Building blocks for people who write code for WordPress every day.