Modx Gallery Upload Event

Hello everyone There is a website on modx. I use the Gallery and PhpThumbOn plugins. I want to connect webp images to the site. modx has a system event OnFileManagerUpload which is triggered when a file is uploaded via a standard file manager:

<?php
    if ($modx->event->name!='OnFileManagerUpload') 
        return;
        
    $file_info=pathinfo($files['file']['name']);
    $ext=strtolower($file_info['extension']);
    $dir=MODX_BASE_PATH . $directory;
    $file=$dir . $files['file']['name'];
    
    if (($ext=="jpg" || $ext=="jpeg") && $files['file']['type']=='image/jpeg'){
        $img = imageCreateFromJpeg($file);
    }
     
    if ($ext=="png" && $files['file']['type']=='image/png'){
          $img = imageCreateFromPng($file);
    }
    
    imageWebp($img, $dir . $file_info['filename'] . '.' . 'webp');
    imagedestroy($img);

This works (images are converted to webp), but only when uploaded via the standard file manager:

But if I upload via the Gallery plugin a copy of the jpg (in webp) does not created.:

Question: How do I create an event so that the plugin works when loading from Gallery? Or which event should I use if it's already built in? I didn't find anything about Events in the gallery documentation

Thanks!