Not able to add option in Sub-Menu under page

Well, the “Enhanced media library” plugin doesn’t follow the Settings API,
just because of this you can’t enhance the plugin options using Settings API.
But you can use Jquery to add the option to any section of EMB or you can create your own custom page or can add options in “WP MEDIA SECTION” using settings API.

I am sharing the Jquery code in case you still want to add options inside EMB pages.

add_action('admin_head','custom_aenhaced_media_manager_js'); 
if ( ! function_exists( 'custom_aenhaced_media_manager_js' ) ) {
function custom_aenhaced_media_manager_description_handler_js()
{
    global $pagenow;
    if( $pagenow == 'options-general.php' && ($_GET['page']=="media-library")){
        $wpuxss_eml_lib_options = get_option( 'wpuxss_eml_lib_options', array() );
      
    ?>
    <script type="text/javascript">
    jQuery( document ).ready(function() {
        let description_status="<?php echo $wpuxss_eml_lib_options['hide_the_media'];?>";
        var html="<tr><th scope="row">Image Description</th>";
        html+='<td><fieldset>';
        html+='<legend class="screen-reader-text"><span>Include children</span></legend>';
        html+='<legend class="screen-reader-text"><span>Include children</span></legend>';
        html+=' <label><input name="wpuxss_eml_lib_options[hide_the_media]" type="hidden" value="0" /><input name="wpuxss_eml_lib_options[hide_the_media]" type="checkbox" value="1" ';
        if(description_status=="1")
        {
            html+=checked="checked";
        }
        html+=' /> Show description under caption on single images in articles</label>';
        html+='  </fieldset>  </td>';
        html+='</tr>';
        jQuery('#wpuxss-eml-form-taxonomies table:first > tbody > tr:last').after(html);
    });
    </script>
    <?php
}}}

In case of any issues let me know.
Make sure to change wpuxss_eml_lib_options[hide_the_media] according to your section and tabs.