Context example

add_filter( 'genesis_markup_content_close', 'insert_html_after_content_markup', 10, 2 );
/**
 * Appends HTML to the closing markup for .content.
 *
 * @param string $close_html HTML tag being processed by the API.
 * @param array  $args       Array with markup arguments.
 *
 * @return string
 */
function insert_html_after_content_markup( $close_html, $args ) {
    if ( $close_html ) {
        $additional_html = '<div>New HTML</div>';

        $close_html = $close_html . $additional_html;
    }

    return $close_html;
}