The difference when using multiple PCs is that you can't put it on the window switch functionality because there's no window switching.

You can still get the same thing, though. For example, you can make "slots" out of Action Target Groups just by placing one Character from each Set in an ATG to signify each slot. Call them "slot1" "slot2" and so on, then put your guy from PC1 in the slot1 group, the guy from PC2 in the slot2 group, etc. Then you can have exactly what Ualaa described, except that your "x toon is master" mappings need hotkeys, and instead of selecting "Slot:1" you use the equivalent groups. Technically only one hotkey is needed, but it's easier to set it up by putting a different hotkey on each of those keys.

To set it up for single hotkey, the trick is to use a virtual mapped key. You'd create a Mapped Key with the hotkey, which just has a Do Mapped Key Action. This Do Mapped Key Action would perform a virtual mapped key, with the Target being Window:Current (self). The virtual mapped key itself is just another mapped key with nothing required (no hotkey, no actions), but you could add a Popup Text Action to it in case you forget to virtualize it for some character, then you could get a visual warning. Then you go to each of your Characters and click on Virtual Mapped Keys, and set it up so that the two boxes there for your virtual mapping read something like this: "virtual i am leader" is now "slot1 is master" (where the first one is your empty mapped key, and the second one is the individual master change used by that toon). When you press the Hotkey, it's going to read that and perform "slot1 is master" if you're on that guy, "slot2 is master" if you're on the next guy, and so on. Same hotkey on all.

Similarly, for people who play on 1 PC, the virtualized mapped key can be used for all Slots in your Character Set instead of selecting the slot 1 master, slot 2 master, slot 3 master, etc individually per Slot.