GraphicEdit

End Page Slide Box is to have an element in the page when you hit the bottom of an article that triggers Slide Box to appear and displaying related article.
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End Page Slide Box

End Page Slide Box is to have an element in the page last paragraph that triggers End Page Slide Box to appear.

Tanmoy

The normal Text widget allows you to insert arbitrary Text and/or HTML code. 
This allows that too, but also parses any inserted Shortcode and PHP code and executes smoothly.
All Shortcode must be enclosed in the standard [ and ] tags for it to be 
recognized. 
All PHP code must be enclosed in the standard tags for it to be 
recognized.

WP Sidebar Essential

Like the Text widget, but also allows working PHP code and shortcode to be inserted.

End Page Slide Box vs WP Sidebar Essential