At present, when a heat map is generated under Impact tab, its axis items are in no sequence /order. Ideally, the x-axis should display items in ascending/descending order of Impact count. It'll be best if there could be an 'Order By' kind of option for the user to decide on which basis they want to view the heat map visual.
Since Heat Maps are visualizations, not having this feature renders an unorganized heat map ineffective in its purpose.