Document name is "read only" and relative to file name or - in case of unsaved docs - set according to application local scheme (i.e "Untitled-13")
What is the reason you want to set this name? Just for display?
The new document is created based on an already open. The user can examine it and take a decision to close or save. It will be more convenient to define the name of the source.
The ideal would be something like this:
or create from a template:
app.open(myFile, true, OpenOptions.OPEN_COPY, "myDocument");