I tried starting the slave with ./jackd -R -d net -C 4 -P 4. Now I can see the 4 inputs/outputs under system on the Laptop and under Laptop on the raspberry pi. However on the Laptop the pi still doesn't show up, and if (on the Pi) I connect the Laptop inputs with the system outputs still nothing happens. (On the Laptop I have a Virtual Audio Cable as default input and output device, so everything thats played via this appears on the other end on the virtual cable as input).