ADDARCHIVES works, CHOP works, INTPARSE works, but CREATEFILTER does not, or at least I still get only "*.xml" as a suffix in the "File Patterns" box.
I found out why this doesn’t work: In the database creation dialog, CREATEFILTER depends on the input format (XML, JSON, etc.). It is always overwritten when the dialog is opened and when this value is changed. Well… I’ll think about that.