I have a USB KVM switch. I also have a Roccat mouse and keyboard. However, these don't work with the KVM very well. If they're plugged into the keyboard & mouse ports, the extra features of the devices no longer work. If I plug them into the KVM's USB hub pots, they work fine, but I lose the keyboard switching ability. If I split the USB into two plugs, with one going to the Keyboard port and the other to the hub port - so the KVM can see the keystrokes it needs for switching, while still passing the full USB signal through the hub to the computer - would this work?
That can't work. There's no multipath support in USB and it's absolutely impossible to use a device with multiple hosts at the same time. Because there's bidirectional communication involved in essential processes like device detection, a device can only talk to one host.
The KVM switch is a host, otherwise it couldn't (efficiently) intercept keystrokes.