compare.lexicon.php - A super useful script for people that want to update translations for MODX (or MODX Extras) and need to get a good at a glance view of the changes. Got it from the forums somewhere in the past, but can't find the original source now. It probably changed a bit over the years too.

compare.lexicon.php

<?php

$default = realpath(dirname(__FILE__).'/core/lexicon/en').'/';
$local = realpath(dirname(__FILE__).'/core/lexicon/nl').'/';
$showSame = false;

// find default files
$theFiles = array();
if($handle = opendir($default)) {
    while(false !== ($file = readdir($handle))) {
        if($file != '.' && $file != '..' && is_file($default.$file)) {
            $theFiles[] = $file;
        }
    }
    closedir($handle);
}

sort($theFiles);

// compare
$_lang = array();
foreach($theFiles as $filename) {
    // load the local file
    if (file_exists($local.$filename)) {
        require_once($local.$filename);
        $localLang = $_lang;
        unset($_lang);
    } else {
        echo '<strong>'.$filename.'</strong><br />&nbsp;&nbsp;&nbsp;&nbsp;<span style="color: red;">File '.$filename.' does not exist in translated file</span><br /><br />';
        continue;
    }

    // load the default
    require_once($default.$filename);
    $defaultLang = $_lang;
    unset($_lang);

    echo '<strong>'.$filename.'</strong><br />';

    // compare keys
    foreach ($defaultLang as $key => $value) {
        if (!isset($localLang[$key])) {
            echo '&nbsp;&nbsp;&nbsp;&nbsp;';
            echo 'The key <span style="color:red;">"'.$key.'"</span> <strong>doesn\'t exists</strong> in translated file<br />';
        }
        else if ($showSame && ($localLang[$key] == $value)) {
            echo '&nbsp;&nbsp;&nbsp;&nbsp;';
            echo '<span style="color:gray;">The value of key "'.$key.'" is the <strong>same as the default</strong> ';
            echo '(<strong>'.strip_tags(substr($localLang[$key], 0, 40)).'...</strong> vs. <strong>'.strip_tags(substr($value, 0, 40)).'...</strong>)</span><br />';
        }
    }

    foreach ($localLang as $key => $value) {
        if(!isset($defaultLang[$key])) {
            echo '&nbsp;&nbsp;&nbsp;&nbsp;';
            echo 'The key "'.$key.'" exists in the translated file, but is <span style="color:blue;">removed by the default</span>.<br />';
        }
    }

    echo '<br />';
}

?>

There's also http://forums.modx.com/thread/?thread=51022&page=1 which looks useful