How do you maximize the coverage of habitable areas?

Solution 1:

Desert: 100 patches (the whole planet)

Deserts don't need mountains to exist. After a mountain has been created it can be leveled with The Ocean Giant and the desert will remain. This way you can cover the whole planet in one big desert.

Forest or Swamp: 69 patches

Forests and swamps has to be placed on hydrated land. The default ocean of 9 patches will hydrate 13 patches of land on either side of the ocean. Bigger oceans hydrates more patches. The formula is:

hydrated patches = 2 * ocean patches + 8

By making an ocean that is 31 patches we can hydrate 2 * 31 + 8 = 70 patches of land which will cover the rest of the planet. We lose one patch due to overlap, hence 69 is the best we can do.

Broken Forest or Swamp: 76 patches

The smallest I have been able to make an ocean is 6 patches. If we want to maximize the number of hydrated patches on the planet we could use four oceans of 6 patches each which will hydrate 80 patches (of which we lose 4 patches from overlap). But this area would not be unbroken.

Another interesting option is two oceans of 14 patches each which will hydrate the rest of the planet (72 patches) with no overlap.

All this is based on a planet with 100 patches which is currently the only one in the game.