iPad as extended display - how to DISABLE?

I'm running Ventura 13.2.1, and I recently started using an iPad in my office (the iPad stays on permanently and is connected to the computer via USB). Well, the Mac keeps thinking it should be an extended display, which is a welcome, but unwanted feature.

So I go into System Settings > Displays, and in the top pane, I see the iPad appear. I can click on it and click Disconnect. But every time I move my mouse to the left side of the screen (where my dock is), the iPad reactivates as an extended display!

How do I switch this feature off permanently? I don't want it.