After closing an HMI screen, how do I re-open my HMI screens from the real-time viewer?

From the Windows Pulldown menu, select “Custom Views.
Right-click on the first line of the Tree view and select Add a View and then select HMI view. From the dialog, click on the button with 3 dots “…” to choose the desired HMI screen.
You can use the same name or type in a new name for your custom view.
Double click and drag this view to one of the docking hotspots.