Matthew, could you place “sell to close” immediately beneth “buy to open”, to have the long entry and long exit togather, and the short entry and short exit togather, and place a line between the two sets.
Ideally, there would be four buttons, one for each action, with the long trade buttons side-by-side, and the short trade buttons side-by-side, to avoid hitting the wrong thing when going fast. I recommend this latter suggestion.