Buck has a mod to do this (but more involved)
https://forums.galciv3.com/475516/page/1/#3621318
the quick way is what exelsis said, just FYI
for more planets you need to DECREASE (not increase) <PlanetFrequencyExp> and for more habital increase the<HabitablePlanets> values
Note habitat is ~ Toral # of planets, so just increasing one ahile not decreasing the other may noy get you where you want to be
Note2: It the fommulation is more complected than just those two variables which is why i gave you Buck's link
