OK, so that plugin if it requires a widget area, then you could add this PHP snippet to your site:
function db_menu_bar_items_widget_area() {
register_sidebar( array(
'name' => 'After Content Widget',
'id' => 'after_content_widget',
'before_widget' => '<div>',
'after_widget' => '</div>',
) );
}
add_action( 'widgets_init', 'db_menu_bar_items_widget_area' );
add_action('generate_after_content', function(){
if ( is_active_sidebar( 'after_content_widget' ) && is_page() ) : ?>
<div id="primary-sidebar" class="menu-sidebar widget-area" role="complementary">
<?php dynamic_sidebar( 'after_content_widget' ); ?>
</div>
<?php endif;
});
It will create a Widget Area after the Content on all pages, called: After Content Widget
Then you can try adding that plugins widget there.
Let me know.