This example will set the strings to be translatable by multilingual plugins.

add_filter( 'frm_form_strings', 'add_form_strings', 10, 2 );
function add_form_strings( $strings, $form ) {
    // Add edit and delete options.
    if ( $form->editable ) {
        $strings[] = 'edit_value';
        $strings[] = 'edit_msg';
    }

    $strings[] = 'prev_value';
    if ( isset( $form->options['rootline_titles_on'] ) && ! empty( $form->options['rootline_titles_on'] ) ) {
        $strings[] = 'rootline_titles';
    }

    return $strings;
}