Here's a wide shot, cable managment with simple velcro ties.
Inside the lid. Had to really cram all this in there carefully. Swapping between SMX and the PC is just a matter of pushing each of the three buttons on the switcher boxes.
Close up of the three switch boxes with labels. They're simple, unpowered pass-thru USB switchers, and a basic HDMI switcher. The audio is shared via a pair of simple RCA Y-adapters (one for each channel) which just combines the audio feed from both machines. I unplug the SMX box when using the PC so audio doesn't come through.
You can use this amazon list to get the same parts Bring your own HDMI cables (a very short one from SMX to the switch, and a normal one for PC) or buy some with the rest of that.