WenZe

Category Parent Children Selector is a WordPress plugin that helps you in selecting parent-children categories.
Features include:
<ul>
<li>Button to select all categories. </li>
<li>Button to select all categories including children categories. </li>
<li>Button to select first level of children categories only. </li>
<li>Button to select parent and all its children categories under its sub categetory. </li>
<li>Auto select parent categories when a sub category is selected.</li>
</ul>

Category Parent Children Selector

Helps you in selecting parent-children categories.

hildende

With installing this plugin you add functionality to <code>wp_nav_menu()</code> to show 
only children of the current page or start with a specific navigation level.

Child Navigation

Adds support for child navigation to wp_nav_menu()

Category Parent Children Selector vs Child Navigation