IS Boxer creates a macro, which loads any macro's made in IS Boxer Toolkit into warcraft.
Besides IS Boxer, you should have the addon Jamba, for the software to work optimally.

When you switch from one window to another, you have several general options.
a) Just switch.
b) Switch and have Jamba update the master (would at least do this, if not A).
c) Switch and have the slaves follow the new master (I like this option myself).
d) Switch and have the slaves strobe-follow the new master (don't like auto strobe follow).

Everyone has their own preference of what happens on a switch.

You can configure it in IS Boxer Toolkit.
Click on your character set in the top pane (expand Character Sets, via the + ).
Click on the 1, on the left pane.
On the right pane I have, (checked) When I switch to this character, and (selected) Do this Mapped Key.
My mapped key is Control Keymap and Follow/Jamba Master.
But you can pick whatever options you want here.

When you switch from one toon to another, the follow can be automatic.




As far as the mapped key action, for FTL Follow Me.
You can assign it a hotkey, or you can have another keymap call this function.
Quite a few of the keymaps call one of the three FTL keymaps (FTL Follow Me, FTL Target Me, FTL Assist Me).

I generally use the Toggle Jamba Follow Strobing keymap to activate follow.
If I just want follow, I press it twice in succession.
But quite often I also want it to strobe.
I gave it the MR button (G15 keyboard light) as the hotkey.
But any hotkey works.