Currently the call number splitting seems to be mostly implemented for DDC and LC classifications. Those are both not very common in Germany and possibly other countries. A lot of our libraries use their own custom classification schemes so the call number splitting is something that should be individually configurable.
One option would be using a regex expression, that can be set in the layout additional to the standard splitting offered by the checkbox.
(see bug 2500 for some discussion about the splitting algorithms implemented atm)
For background information, see: