It’s in the plansAnother thing I want to point out is that the Extron is not a swiss army knife type of solution. I use my Extron mainly for my Apple IIGS to display on a modern VGA or HDMI monitor through appropriate cables and adapters. If you want a swiss army type solution that will have so many options, get the RGB2HDMI.
I have heard this version (590-0322-A) of the adapter allows you to use a IIgs video output with the Extron (more info here: https://www.apple2faq.com/apple2faq/iigs-to-hdmi-using-an-extron-rgb-hdmi-300a/ ) Any chance you could map out the pins on the adapter so I can try to make my own adapter?DB15 to VGA should work because that is what I have, although I am using Apple part number 590-0322-A. But what are you connecting from Extron to the monitor? HDMI to HDMI?