On the monitor that I share with my laptop/desktop, I use a switch.  When I want to switch between PCs, I just hit the button on the switch.  They run around $10 - $20 on amazon. 
I've tried factory resetting, disconnecting power/cables, new HDMI cable, updating drivers/Windows, tried two different pcs and multiple restarts/shutdowns and still the HDMI won't work. During all the troubleshooting my DisplayPort also managed to stop recognizing the connection, but an update on that work laptop fixed the issue. I reserve the DP connection for work and the HDMI for my tower PC Any ideas? I really need this to start working again.
AW3420DW, HDMI stopped working/recognizing connection from one day to the next