I did some experimenting. I tested with a Filco Majestouch-2 and the NovaTouch.
When connected to the rear USB port on the KVM switch, each keyboard works fine. The LEDs on the Filco blink when I switch the switch's internal USB hub between machines.
When connected to the dedicated kbd port, only the Filco works, and the LEDs do not blink when I switch context. Furthermore, the switch seems to keep track of the state of the lock keys separately for each context. In other words, I can have Caps Lock and Num Lock on in one context, and only Num Lock on in the other, and the switch sets those lock states appropriately as I switch back and forth. If I try to connect the NovaTouch to the dedicated keyboard port, the mouse freezes, there is no keyboard input, and Windows will complain that an unrecognized USB device has been attached and that it will not function.
I should also point out that this KVM switch has two hardware buttons that are used to switch between machines. By pressing the left button, context switches to machine 1. By pressing the right button, context switches to machine 2. If I hold down the left button, the USB hub switches over to machine 1, and if I hold down the right button, the USB hub switches over to machine 2. Consequently, I can have the keyboard/mouse/monitor/audio switched to machine 1 while the USB hub is independently switched to machine 2 (or vice versa).
If there is a softkey for switching, I don't know what it is and I never use it.