OK, wow...
I have a meeting going on my MacBook Pro (just watching) and am working on my Mac Studio next to it.
I happened to drag my mouse over and it ended up on the laptop...and the keyboard works there too when the mouse is over there.
🖥️ + 💻
I knew I could do this with an iPad (sidecar) but I had no idea I could trivially use both my desktop and laptop at once 🤩