I've seen where it is possible to emulate keystrokes with a pi-zero, but is there an addon that exists that would allow me to connect a raspberry pi 4 to a laptop and send keystrokes from the pi to the laptop?

As I understand it, you have to tunnel over SSH to get VNC working from outside of your local network. I have followed the steps from a previous topic (http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=24378) but I am unable to get it to work. That and the user that was requesting help didn...