I wrote a script to set up USB device passthrough for a specific device by name to a specific VM by name in the same basic way the XCP-ng Centre UI does it when you follow the steps described in the original post. Here's the script: https://gist.github.com/gpoole/c89807e9de9cb5c87bbcc2da27e0c3e4
Are those the commands you're looking for @olivierlambert?
Either way hopefully useful to anyone who wants to do this without using XCP-ng Centre. I've found it needs to be done every boot, so the script is intended to be something I can quickly SSH in and run. I'm sure it could be automated properly but works for me.