Among the many changes in WordPress 4.4 in an effort to clean the interface, the Get Shortlink button is hidden from view. If you want to restore the button, check out the Shorter Links plugin developed by Rob Allen.
In addition to restoring the Get Shortlink button, it gives users the ability to use custom text that overrides the default URL.
If all you need is the button without additional functionality, the Bring Back The Get Shortlink Button plugin by Thorsten Frommen, is a great alternative with a descriptive name. To restore the button without using a plugin, add the following code to your theme’s functions.php file.
add_filter( 'get_shortlink', function( $shortlink ) {return $shortlink;} );
Get Shortlink is a good example of WordPress hiding functionality without removing it. This allows developers to create plugins like those mentioned above to cater to users who rely on the button’s existence.
call me slow but i really don’t understand how adding the button back actually provides any additional functionality. As far as i can tell it just adds an extra click.
Also not sure how the custom text is different from the edit button.