Hi Brice235i,
I think this may be a SharePoint issue. For security purposes, XML files aren't automatically opened. You could look at automatically converting the file to a link that points to the contents in a document library. We have a popular plugin called qRules that supports that. Then, you can manually modify the link to be use "file:\\" protocol and that should open the form in non-read-only mode in the taret app.
Please email support AT qdabra dot com for more assistance with this approach.
Thanks!
P