Hi,
As I said before, the height of the box expands automatically when you add more elements. So I don't see how allowing you to expend the height manually would help see more products / categories since you already see all the selected ones in it.
So I don't see why we would do that.
Or maybe you're talking about the selection area that pops with the categories tree below the main box ? If you want to increase its height, you can do that easily with a bit of CSS added in your backend:
div.namebox-popup div.namebox-popup-container {
height: 300px !important;
}