But then it would get annoying if you have a laptop with multiple identical ports. You'd have to remember which port you need to plug each monitor into.
Exactly. USB devices do this (seem to identify the device by (port, uuid?)) and it's highly annoying having to rearrange everything so the USB-to-serial adapter can reach the correct USB port so I can keep calling it COM5 and not have to switch everything over to COM1 or COM13 or whatever.
It also causes weirdness like "my scrollwheel scrolls in one direction when plugged into my laptop and the other direction if I plug it into the USB hub in my keyboard."
*on Windows. On macOS USB serial devices use their serial (lol) numbers or models or whatever for /dev/usbserialXXX, definitely regardless of which port you plug it in.
Keys don't need to be defined by a single component - use the monitor reported value, and failover to something like (reported_value ^ connected_port) if there's a collision.
