The export plugins available, i.e. the native xml export and the ONIX export (if I’m not mistaken), do not seem to be very helpful in this regard. The structure that comes out looks quite different to the Crossref xml. So, no I don’t think there are any options to either using the web deposit form or writing the xml manually.
I would be interested to know if anyone knows of a quick way to write up the xml-files. When submitting chapters it can take a while. I’ve used Visual Studio to do this and it’s slightly faster for me than using the web deposit form, but still kind of slow.
All the best
Magnus