Is it possible to keep the mouse and keyboard active when AIO is in HDMI mode?

I am using an Optiplex 9030 All-in-One machine. I have a second computer and have connected both computers to a KVM switch so I can easily switch between the two. The problem is that the switch obviously can't change the video setting from "Computer" to "HDMI In" automatically, so I would prefer to use my other monitor as the one that switches.

However, it seems that whenever the AIO is in "HDMI In" mode, the keyboard and mouse inputs are disabled. I can see why this might be done, but it's still not very convenient. I'd like to know if there is any way to disable this feature so that I can keep using my mouse and keyboard on the other monitor. I looked for BIOS settings, but I didn't find anything obvious. Does anyone know how to fix this problem?

Thanks!