The new 8-channel Kiwi configuration mode trades two of the zoom waterfalls for the ability to have an extra 4 audio-only receiver channels. I.e. the original RX4/WF4 mode, where each receiver channel was paired with a waterfall, can be replaced by an 8RX/2WF mode where only the first two channels have a waterfall. The other 6 channels get a blank waterfall and spectrum display (see this post:
http://forum.kiwisdr.com/discussion/1233)
The v1.221 release now adds an audio FFT in place of the zoom waterfall / spectrum for those channels that were formerly blank. This is possible because all the FFT processing is done in Javascript on the browser. No additional FPGA, Beagle or network bandwidth resources are required.
However, this scheme has its limitations and also a number of known bugs that are being worked on. When I have a little more time I will list them. Until then please give the audio FFT a try.