You can't make a parallel spline, but you can do an offset with line-tools.
1. Choose tool, Line or Polyline
2. Press "Relative construction method" and choose Offset tool (icon number 4)
3. Release mouse button, and this tool should be marked, if it's not, press the button again.
4. Press Space-key on your keyboard and you se your "Magic wand tool" mouseicon on screen, hold this key down and click with your mousebutton on your spline
5. Drag your new line / polyline at right direction, press R-key and type your distance and press enter
Done! (I hope)
