You can change the size of the font for any category of celestial object. For example, in Options ---> Solar System ---> Planets-Moons <--- if you put the cursor over the word "Planets-Moons" you will see a rectangle surround the word. This means it is clickable, there is a sub-menu. Click on it, and when the sub-menu opens you will see an option. at the bottom of the panel, to change the size of the font.