There is a hotkey to switch between multiple monitors, but keep in mind that on the host, you first have to select or select a window with actual content to be able to switch between monitors. If you select the desktop on the host monitor or the header of the remote control window itself, then you won't be able to switch to another display.

To switch displays, hold down the left CTRL key + left Windows Key, and use the left and right arrow keys to cycle through the available displays. The "All Monitors" option is part of this cycle as well.