I want to triple-boot Lion, El Capitan, and WIndows. Howto?
iPartition used to be the go-to tool for this kind of task, but it cannot handle Core Storage volumes, which makes it a bit limited these days.

Paragon have just brought out a new Hard Disk Manager which I have yet to try out for myself, but looks like it's the long-awaited successor to iPartition. Personally, I don't think the interface looks as good, but you can't have everything ;-)

Both apps require you to boot from an external device to work on the boot drive, of course. Paragon has a built-in boot drive creator, I can't remember whether iPartition does [it had a CD maker, back in the day, but I've not used it in quite a while]

For your particular scenario - I'd clone off one of the Mac partitions, re-partition as a single Mac volume [plus EFI/Recovery of course] then let Bootcamp do its regular setup. Afterwards, resize then add a new partition to clone your 2nd OS X back to.