Joseph Wright writes:
 > Hello,
 > 
 > I was wondering why \exp_args:NNNo wasn't listed in source3. 

being added later (probably when I or somebody else needed it) .. there are
probably more that are missing completely or at least in the documentation
part.

 > A look
 > through l3expan shows it is defined: could it go on the list?

done and uploaded

frank