How to stop annoying informative gray area to appear in Altium?
As shown in the heads-up display (HUD), Shift-H toggles it on/off. If you press the key combination Shift-H it will hide it. You can also access this control by going to the "View" menu, go down to "Board Insight", and uncheck "Toggle Heads-Up Display". Note that you must be focused in the PCB editor for this shortcut or menu navigation to work.