Ok, I see. Being able to copy nodes (and their children) on mobile would be a valuable feature for me. I have a template that I make a copy of as part of my daily routine. It's easy to do on desktop, but it sounds like I can't do it on mobile yet.
I'm not using an external keyboard with my phone, but I do sometimes use the excellent Hackers Keyboard, which allows one to send key commands as though one were using a regular keyboard. That's how I knew that Ctrl-Sh-M works on mobile.
I'll start a new item in the Feature Request section. Thanks for your answer!