ShinichiN

This plugin enables you to create unlimited custom sidebar/widget areas and switch existing areas. You can do this without touching your theme.
This plugin utilizes term meta api and so it works only with WordPress 4.4 and above.
Your theme needs to use <code>is_active_sidebar()</code> when calling <code>dynamic_sidebar()</code> function.
This will work.
<pre><code>if ( is_active_sidebar( 'sidebar-1' ) ) {
 dynamic_sidebar( 'sidebar-1' );
}
</code></pre>
This doesn’t work.
<pre><code>dynamic_sidebar( 'sidebar-1' );
</code></pre>
If you only want to output your custom sidebar, put this code on where you want to display the sidebar in your theme.
<pre><code>do_action( 'dynamically_dynamic_sidebar' );
</code></pre>
<a href="https://github.com/ShinichiNishikawa/Dynamically-Dynamic-Sidebar/" rel="nofollow ugc">This Plugin published on GitHub.</a>
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Dynamically Dynamic Sidebar

Create unlimited custom sidebar/widget areas and switch existing areas depending on post, page, custom-post-type post, categories, tags and custom tax …

iniyan

Logesh Kumar Rajkumar

Scroll Triggered Widget is not an actual widget. It defines a new widget area when activated. You can drag and drop any widget you wish like a normal widget area. The widget area gets triggered when you scroll down to the bottom of the page by default. But you can control the location where it gets triggered in the plugin options page. The plugin comes with lot of customization options.
Plugin features 
– 25 unique animation effects 
– Change the background color of the widget 
– Change the Border color and width 
– Choose where the widget should display 
– Drag and drop any widget of your choice 
– Controll how long the widget area should be remain hidden when closed 
– Users can click the moving arrow in the bottom to revert the widget area

Scroll Triggered Widget Area

This plugin triggers a widget area when a user scrolls down the page. It comes with more than 20 animation effects and more customization options.

Dynamically Dynamic Sidebar vs Scroll Triggered Widget Area