Unfortunately, I think you are right about doing it manually. The “cleanest” solution I can think of is using a filter and parameter sweep and run simulations with the filter moving from wavelength to wavelength. You could then plot the BER as a function of center wavelength of the filter. As of right now though we do not have a WDM Receiver.
The other more involved solution would be to scripting. It should not be that hard to create any number of BER Analyzers and then save the BER and wavelength data.
Regards