For IS Boxer, in the lower right pane, right click on actions.
Select: Keystroke Actions > New World of Warcraft Macro Action.

Choose the target normally, but you need to set a Keybind Option.
This is not the hotkey for the mapped key which will run this macro.
It has to be a unique keybind, which is not used for anything else.
When in warcraft, this macro can be run via that keybinding.
But, the mapped key which does this macro can be a lot simpler.
The macro box will let you know if you have other macros which use the keybinding for the macro.

You can use FTL options in the macro, including assist or target the active toon before the macro.
And optionally, restore original target after the macro.
Optionally, you can name the macro, for use with /Click based macros too.