Hello Harke,
It is possible to make complex port impedances by using complex Z function of S parameter block. You can read more here: https://qucsstudio.de/forums/topic/simulation-of-s-parameter-matrix-with-complex-port-impedances/
It is janky and I do not think that there is a scriptless way to modify it without editing the touchstone file manually.
I really hope this feature comes in the future.