Used to be if the capital is in a tropical province you'd escape the maluses for all tropical provinces you own. As of the betas the income related maluses to tropical provinces are removed anyway though so I'm guessing it's not as good a move from an economical point of view as it used to be.
I added a region for all tropical provinces in my game to see where they are more easily, other than that you can see it in the tooltip for the various values in the province view (as a modifier).
I added a region for all tropical provinces in my game to see where they are more easily, other than that you can see it in the tooltip for the various values in the province view (as a modifier).