How to change the whitecapping coefficient Cds in Delft-Wave

I have worked about the wave calibration in these days, and I met a problem that the significant wave height from Delft-WAVE is much lower than the observation data. I have searched for ways from the user manual and google, and found an advice to change the whitecapping coefficient Cds. However, in Delft-WAVE GUI of Windows, there is no place to change Cds. The Cds is the default data and can not be changed in Delft-WAVE. I know that Delft-WAVE is based on SWAN, and in the independent SWAN can change Cds in the .swn file. However, I want to run DelftWAVE module together with DelftFLOW. Is there any way to change the Cds in Delft-WAVE? I will very appreciate if you can give me an advice There is the picture from the user manual.