The manual states:
This is fine but does not entirely explain the usefulness of this function.
However, in the absence of the ability to assign Custom Modes to function buttons (like Mysets on the E-M1) to switch quickly between shooting modes in various shooting scenarios, the Set Home can act as a toggle switch. Whilst designed to return to your home settings it actually can be used to switch between separate Focus Modes and Focus Targets.
This allows using the Fn Lever for another purpose.
It’s a bit tricky but here is how I have set it up for my Custom Mode 1.
Now press the Fn1 button and it should switch to S-AF + MF/Single point (s) with HP icon flashing on SCP. It is important to save this setting to a Custom Mode otherwise it is easy to lose the toggle switch (see note below).
Note: If you move the focus point in the target area while shooting a long press of the OK button will make the target point revert to the home position. But you will lose the toggle switch between the Focus Mode/Target Mode. As long as you have this Set Home setting saved in a Custom Mode, switching the camera off/on or moving the Shooting Mode dial to another position/back will get the toggle switch reactivated.
I saved this setup to my Custom Mode 1 as part of my Static bird setup and have other configurations for my other Custom Modes.