Some tools never disappear; they improve over time.
I created the KC Tools WP plugin a long time ago for my own work, and I still use it. From time to time, I add another useful feature. I have now released a new version so that everyone can benefit from the latest tools.
For site users, the plugin includes a "Debug Email" function. They can send diagnostic information from a page on their site to the email address configured in the plugin.
For administrators and developers, it includes a hidden function for displaying the $_SERVER array.
The most powerful improvement is in the DB tab. The plugin can now recognize serialized data stored in a database result cell and display it in a readable format.
I hope these additions are useful.