Yes, I used a hardware KVM with a laptop (Dell with a dock) and a desktop, it makes a lot of wires, but it works.

But having both system at the same time is a must, so at one point I used RDP (windows->linux or linux->windows) from a screen.

But for ~3 years now I’m using a software “KM”, meaning my desktop is connected to a monitor, my laptop is connected to the second monitor, and I share the keyboard/mouse (hence KM) in software using InputLeap (formerly Barrier). It is seriously pretty good, when my mouse exit monitor #1, it enters monitor #2, and whatever you type is entered in the system where your mouse cursor is. It is fantastic, I cannot live without this now.