To reproduce

1. two monitors setup
2. Open the Unity editor full screen in the secondary monitor.
3. In your primary monitor, dock the taskbar at the top of the screen
4. In the editor, undock the inspector by clicking the inspector and drag it under the taskbar. You'll find the dock doesn't check the workarea.

Note: New panels typically will open under the panel like this. And it forces you to hide your taskbar to get the top of your IDE panel to move it away from the task bar