Rainbowcube - what are the extra parts for?

I have recently bought and mostly assembled the rainbowcube kit. I notice that it comes with some extra parts - a 2x3 female header, JST power connector, male and female headers, etc. These parts are listed in the “kit includes” list, but not mentioned in the documentation.

I think I see a place where the 2x3 could go, but I see no indication of what it is for in the assembly manual or in the wiki. The other parts get no mention.

I’m sure these would be very handy if I understood the kit better. Could someone explain it to me? Thanks.

I have the RainbowDuino v3.0b, which has a 2.1mm power connector. I saw a picture of an earlier version, which has a JST connector in its place. So now I know what the JST power connector was for. It isn’t needed for my RainbowDuino.