zackdesign

Turn your WordPress post categories into a search powerhouse! This plugin gives you a set of dropdown menus based on parent categories and their sub-categories. Users select one sub-category per parent, and the plugin filters posts matching the selected combination.
Available as:
<ul>
<li>Gutenberg Block — “Multi-Category Filter” in the block inserter (new in v4)</li>
<li>Classic Widget — “Multi-Category Selection” in Appearance > Widgets</li>
<li>Shortcode — <code>[mcsw]</code> on any page or post</li>
</ul>
Features:
<ul>
<li>AND / OR category filtering — find posts matching ALL or ANY selected categories</li>
<li>AJAX chained drilldown — selecting a parent dynamically loads its children</li>
<li>Pretty permalink URLs (<code>/categories/3,5/search_type/and/order/title/</code>)</li>
<li>Ordering by title or default</li>
<li>Configurable blank search behavior</li>
<li>Exclude specific categories</li>
<li>Lightweight — no jQuery, no external dependencies</li>
<li>Pagination support</li>
<li>Display form above results on category pages (optional)</li>
</ul>
Sample use case:
Real estate — set up parent categories like “Bedrooms”, “Bathrooms”, “Price Range” with sub-categories beneath them. Users filter listings by selecting from each dropdown.
Upgrading from v3.x:
<ul>
<li>PHP sessions have been removed entirely — the URL now carries all state, which means better compatibility with caching plugins, load balancers, and modern hosting</li>
<li>jQuery has been replaced with vanilla JavaScript</li>
<li>CSS classes have changed from <code>wpmcsw</code>/<code>wpmm</code> to BEM-style <code>mcsw-*</code> classes — update any custom CSS</li>
<li>The old <code>select-chain.js</code> in the plugin root has been replaced by <code>js/select-chain.js</code></li>
</ul>

Multiple Category Selection Widget

Filter posts by selecting multiple categories using dropdown menus. Available as a widget, block, or shortcode.

Murali

WordPress press widget to list category and subcategories of posts/custom taxonomies of custom post types.
Features
<ol>
<li>
It allows users to add custom icons for category or for subcategory or for custom taxonomies
</li>
<li>
It lists categories and subcategories in user-friendly horizontal pattern. Please refer screenshots.
</li>
<li>
Category icons can be edited/removed/update with new icons under edit category or under edit custom taxonomy admin screen
</li>
<li>
Admin settings of this widget has facility control display on/off for category icons
</li>
<li>
Admin settings of this wiget has facility to show/hide count of posts in categories
</li>
<li>
Admin settings of this widget has facility to show/hide empty categories in widget
</li>
<li>
Title of widget can be customized in widget settings
</li>
<li>
Compatible with blocks under widgets section
</li>
</ol>
<h4>My Links</h4>
<ul>
<li><a href="https://www.muraliwebworld.com/groups/wordpress-plugins-by-muralidharan-indiacitys-com-technologies/forum/topic/category-sub-category-widget-for-wordpress-websites-using-php-javascript-jquer/" rel="nofollow ugc">Plugin homepage</a></li>
<li><a href="https://wordpress.org/plugins/push-notification-for-post-and-buddypress/" rel="ugc">Push notification plugin for WordPress,BuddyPress and for Mobile apps</a></li>
<li>Twitter @<a href="https://twitter.com/indiacitys" rel="nofollow ugc">indiacitys</a></li>
<li>Facebook <a href="https://www.facebook.com/indiacitys" rel="nofollow ugc">indiacitys</a></li>
</ul>

Category and Subcategory List Widget


The concept does exactly what I wanted. Parent and child categories are both clickable, and only the parents are initially visible (that's good in the sidebar), and on click the WordPress search results page for the chosen category is displayed. I'm creating a new website for a tour operator, and they have a few tours to the Baltic area, a few to Afrika, a few to Asia... and 20 to Europe. The problem is when the mouse goes over Europe, the flyout child menu is positioned either above or below the parent item, depending on which direction has most space. But always pinned to the parent item. With 20 items in the child menu, it's always truncated (off screen) either at the top or the bottom. It would have space if you instead oriented the middle of it to the parent item - or better, make it equidistant to the top and bottom of the viewport. As is, I can't use it. And all this icon stuff, I don't need it so it's just adding bloat to the CSS sent to the browser. Could you not send it to the browser if icons are not selected?



Anyways, after a good laugh at the German translation of "empty cats" as "leere Katzen" (Katzen are those four-legged meow house pets), I updated the German translation. Look for Tim Reeves, Waldheim, Germany if you want it :)



And thanks for a well-conceived plugin!


Good concept, problem when a lot of child categories

This widget allows to add/update icons for category or icon for custom taxonomy. It lists Categories in horizontal menu pattern.

Multiple Category Selection Widget vs Category and Subcategory List Widget