Labels should include required info, when it's a required field

Temporarily solved it wthis way:

/**
 * Maybe add required span to labels
 */
add_filter( 'rwmb_begin_html', function ( $begin, $field, $meta ) {
 
    if ( is_admin() )
        return $begin;
 
    if ( ! empty ( $field['required'] ) ) {
        $begin = str_replace( '</label>', '<span class="req">*</span></label>', $begin );
    }
 
    return $begin;
}, 10, 3 );

Additional question: Tried to apply this hook only to the frontend submission fields, by using filters/prefixes like rwmb_frontend_begin_html, mb_frontend_begin_html, rwmb_mb_frontend_begin_html but none of them worked.

Perfect, thanks!