By clicking on individual men's names you can see how many had multiple (polygamous) wives... for example click on John Doyle Lee and see the list of wives. Next to each you will see a link for her children.
There are 11 individual men in my family charts that participated in LDS polygamy. I'm related to most of the State of Utah through at least one of them. I suspect the fLDS would use this kind of system to track the individual children born in the polygamous unions.