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 in the plugin root has been replaced by 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

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