I am building a notebook based on a Radxa Zero and a 1920x480 screen (goal is to make it look like a TRS-80 Model 100) and I am stuck on a rather minor thing … is there an equivalent to pin 5 in a raspberry pi?
Using that pin I can turn on the pi (example: https://github.com/Howchoo/pi-power-button)
I’m not sure if the SoC has a similar hardware function, but if you’re building a notebook with battery, you could achieve the same functionality with your battery/power management system. You’d probably want it to power off any other system components too.
Well, the only thing that takes power is the zero (everything else is connected to it).
Yeah, I can just put a dumb switch in the power cable, but that will hard power off. I could do two switches, one for a soft-off using any GPIO and a “cycle power” one that would make it turn on, but … that’s two buttons 
What are you using for power?
A dumb 8000maH power bank
Maybe you can open it up and see if you can identify the controller ic and find the datasheet.