TheHandOfCod

Through the use of the WordPress custom Taxonomy API you can add sub categories to your posts such as eCommerce, Books or Plugins. 
This can be especially useful if you have an eCommerce platform which uses custom post types in conjunction with custom taxonomies.
<h4>Custom Taxonomies</h4>
In case you are not familiar with custom taxonomies there are two parts when you create a custom taxonomy. 
There is the taxonomy itself and the terms associated with that taxonomy. So for the Tag taxonomy, for example, 
the taxonmy is Tag and the terms are the tags which are added to posts. In the case of categories the taxonomy is 
Categories and the terms are each category value which have beed added.
<h4>Features</h4>
The features of the Toolkit are :-
<ul>
<li>Bulk removal of terms from posts</li>
<li>Bulk addition of terms to posts</li>
<li>Taxonomy and term creation</li>
<li>Taxonomy and term deletion</li>
<li>Moving terms from one taxonomy to another</li>
<li>Taxonomy editing</li>
</ul>

Foxdell Folio Taxonomy Toolkit

Have finer control over your taxonomies so that you can have better organisation of your posts by using taxonomies other than just Categories and Tags …

WP Messiah

BoomDevs

Swiss Toolkit For WP

Say Goodbye to Plugin Overload - WP Swiss Toolkit Has It All

Foxdell Folio Taxonomy Toolkit vs Swiss Toolkit For WP