Greg Winiarski

BlackBox is symfony like unobstrusive debug bar attached to the top of the browser window.
How can it help you with development: 
1. instantly inspect global variables (GET, POST, COOKIE, SERVER) 
2. debug both frontend and admin area 
3. executed MySQL queries and time it took to execute each query (useful for finding slow queries) 
4. profiler for measuring performance of your plugins and themes 
5. errors occurred when loading WordPress page

BlackBox Debug Bar

Immediate feedback on a great majority of errors. Added a conditional red background to the Errors, and with this modification I have never miss even a notice anymore.

Thank you very much!

Essential plugin in my developer toolset

BlackBox is a plugin for plugin and theme developers. It collects and displays useful debug information (errors, executed queries, globals, profiler).

10up

Taylor Lovett

Allows you to examine every ElasticPress query running on any given request by adding an <a href="https://wordpress.org/plugins/elasticpress" rel="ugc">ElasticPress</a> panel to <a href="https://wordpress.org/plugins/debug-bar/" rel="ugc">Debug Bar</a> and/or <a href="https://wordpress.org/plugins/query-monitor/" rel="ugc">Query Monitor</a> plugins.
Alternatively, go to ElasticPress > Query Log and set it to record ElasticPress queries.
<h4>Requirements:</h4>
<ul>
<li><a href="https://wordpress.org/plugins/elasticpress" rel="ugc">ElasticPress 4.4.0+</a></li>
<li><a href="https://wordpress.org/plugins/debug-bar/" rel="ugc">Debug Bar 1.0+</a></li>
<li>PHP 7.0+</li>
</ul>

ElasticPress Debugging Add-On

Indispensable if you're working on a site with ElasticPress integration

This plugin works perfectly and is very useful for debugging ElasticPress queries.

It Does What It Says

Extends the Query Monitor and Debug Bar plugins for ElasticPress queries.

BlackBox Debug Bar vs ElasticPress Debugging Add-On