You actually set up a mapped key like this.

Hotkey - Something that will be easy to spam.

Two Steps.
Step 1 - Either an IS Boxer Macro Action, or a Keystroke Action which is your Warcraft keybind for macro A.
Step 2 - Either an IS Boxer Macro Action, or a Keystroke Action which is your Warcraft keybind for macro B.

In practice, you spam the one key.
Which alternates between sending output 1 and output 2.

You never toggle 1 or 2 off.
Unless you have a specific reason for it.
But with the default play, your spam key alternates between one macro and the other.

It isn't so much a toggle as an alternating output.