Find out what WordPress translation text domains an element is using

debug-translations

add_filter( 'gettext', 'debug_translations', 30, 3 );
function debug_translations( $translated_text, $text, $domain ) {
    if ( $translated_text ) {
        $output  = $translated_text;
        $output .= '<span style="font-size: 18px; color: white; line-height: 1; background-color: red; width: 24px; padding: 3px; border-radius: 18px;" title="text-domain: ';
        $output .= $domain;
        $output .= '">�</span>';
    }
    return $output;
}