Add Knowledgebase to WP back end

Hi!

I’m trying to add a knowledge base to the back end of a WP installation. I tried adding the following code to a custom plugin’s main php file:

add_submenu_page('myplugin','Documentation','Documentation','plugin-slug','docs','viewDocs');

function viewDocs(){
	$return_string = require ABSPATH . 'wp-content/plugins/wp-knowledgebase/template/kbe_knowledgebase.php';
	wp_reset_query();
	return $return_string;
}

I didn’t work. Apparently, the template tried to display the page as it were an external page.

Is it just about modifying the template? Or will this never work?

Anyhow, one interesting feature to the plugin would be allowing it to be used on the back end natively.

Any help is greatly appreciated!