Okamoto Hidetaka

This plugin gives you Related Item Widget and function.
If you want to show Related Item List, you can do following actions:
<ul>
<li>Add <code>Elasticommerce Related Widgets</code> in your widgets area.</li>
<li>Add <code>escr_related_item();</code> function in your theme or plugins.</li>
<li>If you only want to get the data, you can use <code>escr_get_related_item();</code> function.</li>
</ul>
Notice 
This plugin requires WooCommerce Plugin , so please install it. If WooCommerce Plugin is not installed or activated, this plugin will not work.
Required 
This Plugin cannot use Elasticsearch version 2.x. Please use Elasticsearch version 1.5 instead.

Elasticommerce Related Items

You can get good Related Item List powered by Elasticsearch.

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.

Elasticommerce Related Items vs ElasticPress Debugging Add-On