Turn Off Switch

[PiZeroNoobie01]

Hey guys, I am planning to build my very first gameboy zero and came across this wiring diagram. I was wondering if I should add a slide switch where I have circled or would it be more appropriate to place it somewhere else? And would I need to install a software to trigger a safe shut down?

Thanks!

Source: https://www.joshendyblog.net/gameboy-pi-zero/