This is a heavily requested feature, for all of the 3 major NCrunch views (Tests Window, Processing Queue, Metrics View). Unfortunately it cannot be implemented at the moment because of the design of the tree component used to construct these views. You'll notice that the tree component has a cell based setup where the left and right cursors will switch between cells - this is at the root of the problem.
In V2, the tree component is being completely replaced, which will not only solve a number of performance issues, but will also allow proper use of the cursor keys. So yes, this feature will definitely be implemented in future :)
Cheers,
Remco