There does not appear to be one - the power setting only accepts True or False. It is designed to be used as a solid excitation voltage for use with digital inputs, not a 5th output.
You could examine the smartplug driver and cut-n-paste the channel subscription portion to the power pin.
I have been working on the DIO a lot lately - connecting 12vdc motion detectors with relay contacts as inputs and direct driving 12vdc landscape lighting fixtures.
The idea is to put ‘auto-night-lighting’ in my new house - all public areas will have these dim lights which automatically come on if anyone moves.