If the computer you're connected to is connected to multiple displays, you can select which display you wish to use with Screens. To do so, use one of the following methods:
Click the Displays button in the toolbar and select the desired layout.
Navigate the Screens application menu: View > Displays > [Layout]
Remember Selected Display
In the saved screen settings, under More Settings, enable Remember selected display to automatically select the last used display for each subsequent connection.
Linux and Windows PCs
Screens’ display selection feature works only with Macs. You can, however, accomplish the same result with Windows and Linux computers by changing the port number in your saved “screen” settings. Choosing a particular port number selects a corresponding display.
Usually, port 5900 is used when Screens connects to your computer. If you have three displays, you may use ports 5901, 5902, or 5903 to specify Display 1, Display 2, or Display 3, respectively. Most VNC clients on Windows and Linux support this feature.
The advantage of using Screen Sharing on macOS is that it lets you select a display on the fly, rather than requiring you to disconnect a Screens session to reconfigure the port number and select another display.