Whoa Bruno, looks like you've put loads of work into this.
Ok I've attempted to go through all the steps and I can now upload files via the multifile uploader and folders are created in respect of the ID of the database. However, images don't always end up in the right folder - when they are moved into the correct folder you can then load from mediasource and the images persist.
I have got the lettings/migxconfigs/resourceablum.config.inc.php still in place as above.
I changed the info in the following code to reflect my settings:
$fields['id'] = $modx->getOption('co_id', $_REQUEST, 0);
$fields['image_list'] = $modx->getOption('name', $scriptProperties, 0);
The following line of data is entered into the database under image_list
[{"MIGX_id":"1","image":"icon-3.png","deleted":"0"}]
At the moment, I haven't been able to access this information. Couldn't get the snippet getmigxcartfilepath to work even with adjusting the file path.
There's currently nothing in the error log either.
But think we're alot closer to achieving a very nifty solution for multiple uploading images in a MIGXdb.