Show/Hide Panels with the Function Keys
Use the function keys F5, F6, F7 and F8 to clean up your Lightroom screen.
F5 controls the visibility of the top panel, F6 controls the bottom (Filmstrip) panel, F7 controls the left panel, and F8 controls the right panel. Pressing any one of these keys will hide or display the appropriate panel.
To hide all the panels, press Shift + Tab. To bring them back again, press Shift + Tab again.