KVM with U3824DW - how does it work

I connected 2 computers to the KVM of the U3824DW: one is a dell laptop, and the other one is Raspberry PI (aka RPI), and a Keyboard and mouth on the downstream USB.

The 2 computers can be well seen on the split screen.

I installed the software on the Dell laptop side, so I can use the KBD and mouth well on the dell laptop, and also transfer the control to the RPI, using a hot key I defined (shift+A)

The problem is that I can't transfer the control back to the Dell laptop from the RPI, maybe because there is no Dell software for the RPI?

Is there a way I can transfer the control between the 2 computers without the Hotkey?