Can a PiP window have a different input?

[zoiman]

I am using the DELL U4025QW with two macbooks (thunderbolt, hdmi+usbc for usb) and I can successfully switch with BetterDisplay between those two which also switches the keyboard/mouse since the monitor has a builtin KVM. This is already more than awesome since the DELL software is... well it did not receive too much love during development I assume.

Now I was wondering if I can use the Picture in Picture when I am connected with macbook A(thunderbolt) but the PiP will get the input of the HDMI?
And if this works somehow, how can I switch just the usb with a keybinding?

So the use case is this:
I am connected with both macbooks to the monitor.
Macbook A (thunderbolt) is beeing displayed on the monitor and mouse and keyboard are working as well.
Now I want to hit a hotkey which opens a PiP which shows me the HDMI output of Macbook B. Mouse and keyboard are still from macbook A.
Now I want to hit another hotkey which switches the mouse and keyboard to Macbook B and I can control the things in my PiP window.

Is something like this possible?