Pressing Ctrl M (Mac: Command M) brings up the Curves adjustment window. Unfortunately this is a destructive command and there is no keyboard shortcut for the Curves Adjustment layer.
To take advantage of this keyboard shortcut and work non-destructively, change the shortcut so that it creates a new Curves adjustment layer instead of opening the Curves window.
To do so, press Ctrl Alt Shift K (Mac: Command Option Shift K) to bring up the Keyboard shortcut menu. Then click on Layer and choose Curves under ‘New Adjustment Layer’. When the input box is active press Ctrl M (Mac: Command M). Accept the change, and close the window.
If you now press Ctrl M (Mac: Command M), you’ll create a new curves adjustment layer.