you are right, there is no power allocation in the simulator. SNR_vec only impacts the noise variance; the transmit power is normalized to one. You can of course multiply your symbols with wathever power you like. However, this will have to be accounted for at the receiver (in the equalizer, the feedback calculation and possibly other places).
As an alternative, I suggest to switch to our 5G link level simulator, which supports power allocation as well as NOMA.