While in DSDPlus window, press R to record the raw audio. Press R again to end recording.
If you do this with the FMP window highlighted, it creates 2 files, .FM and .IQ. I believe this is the raw recording of the entire bandwidth of the SDR in use. It will be a huge file and can easily be gigabyte sized. For example, I just did it and a 2 second recording with a 2 MHz wide SDR created a 18MB file.