I’m not sure what your question is. If you’d like to enable brem splitting in a G4Region, you can define that region in your detector construction. Then use the command in your macro:
replacing ‘target’ with the name of your region. This command is already defined in Geant4, so don’t define it yourself.
You don’t have to define a region. In this case, use “world” as the name of the region:
/process/em/setSecBiasing eBrem world 10 100 MeV
and the splitting will occur everywhere.