Grid and properties pane should probably be similar or identical -- it would be much easier to grasp for the new user, much more intuitive.

 

So that means that Grids should probably adopt ctrl + left/right  to collapse to the immediate parent or expand the currently focussed item/parent... and get rid of the of the ctrl+"-" ctrl+"+". This would make the whole grid navigation much more efficient  : no more reaching for another spot on the keyboard. Leave your hand in the same spots, move items, navigate in the grid, expand/collapse hierarchies.

 

(For more "detailed" operations, Ctrl+numbers OR ctrl+shift+numbers is still perfect. No problem with that.)

 

But maybe are there cons to such an approach... Opinions ?