No, not anywhere
, but somewhere
Why is it important to specify a particular partition?
You should read https://github.com/raspberrypi/noobs/wi ... -explained
that explains how the NOOBS partitioning works. The NOOBC v1.5 onwards section is relevant.
I would suggest using Matt's webpage to choose your OSes including a ProjectSpace or DataPartition to reserve some space, adjust the sizes of the partitions as you want, then let PINN manage the partition creation. After that you can use Gparted to adjust the partitions further if necessary, or just repurpose the data partition or project space partitions for whatever you need. Ideally you should leave any free-space (unused projectspaces or datapartitions) at the end of the SD card if you want to do partition alterations so they not alter the partition numbering of the OSes that PINN has installed, but currently it is not possible to force the ordering of the OSes that PINN installs.
Another (untested, but maybe simpler) alternative is to specify a smaller SD card on Matt's webpage than you actually have. That way only half of the SD card will be allocated by PINN and it's OSes and the rest is available for whatever else you want.