The PLECS small signal analysis tools return a set of gain and phase values. There is no native export from PLECS into a format compatible with Matlab PID tuner.
I see this as a more generic problem that is better suited for Mathworks support. How can one take the gain and phase relationships and then generate a transfer function in the s-domain from that? Once the transfer function is determined, it can readily be imported into the PID tuner block. Perhaps the “tfest” function appropriate for this? Matlab/Octave may have other tools as well.