I think there need to be another column to categorize planet. If you click on a planet, in the information panel it says it common, uncommon, rare and so on. Why aren't they categorize like this, too? I would like this feature added, if possible. Is it cause of a lack of space to add another column?

Planet rarity is pretty much a meaningless category. The only significance of it is how many of that type of planet are in the galaxy, and nobody but Dan knows the actual numbers. Completely not needed, sorry...