Your PiP swaps are:
Shift F1
Shift F2
Shift F3
Shift F4
Shift F5

In a focus approach.
Within warcraft on the Shift F1 keybind, all clients have the macro /Focus ToonA.
Within warcraft on the Shift F2 keybind, all clients have the macro /Focus ToonB.
Etc.

So when you hit Shift F4 and toon 4 is the active toon.
Toon 4 becomes the focus of every toon.

Your one follow macro is:
/follow [target=focus]

Does not matter who the focus is, that's the toon you follow.

DPS casts at the focus's target.
Again doesn't matter which toon is leading.
Your slaves (and active toon) cast at the target of the Focus (active toon).