thevittfile

The plugin looks up the sub-attributes in your product, then for each value it looks up its parent and adds the parent attribute and the parent value in the product. 
When using a filter with the main attribute on the store page, all the products that have that main attribute are returned, which are the same products that contain the associated sub-attributes.
Important: 
You can’t create multiple hierarchy levels, just one. 
Two diferent attributes cannot contain the same sub-attribute.
<h3>Documentation</h3>
<a href="https://github.com/vittfiles/vitt-attribute-hierarchy" rel="nofollow ugc">vitt attribute hierarcht for woocommerce</a>

Vitt Attribute Hierarchy for WooCommerce

This plugin works simulating a hierarchy for attributes and subattributes.

akherati

this plugin enable search field in woocommerce attributes when you add OR edit products. 
If you encounter a very large number of attributes when inserting your product attributes, this plugin is for you so you no longer have to spend time finding one attribute out of hundreds of attributes.
this plugin will add good feature to woocommerce so you must install and active woocommerce plugin before that.

fast select Attributes for WooCommerce

You can search and fast select woocommerce attributes of too many attributes in add product page or edit product page.

Vitt Attribute Hierarchy for WooCommerce vs fast select Attributes for WooCommerce