As I don't know the 'lucy star story', I can't determine who the main character is. But based on the name, it seems that Lucy might be the main character.
Since I don't know the specific 'the belle star story', if it's named as such, the main character is likely Belle Star.
The main character in the 'star thrower story' is the person who throws the starfish back into the ocean.
Since I don't know the specific 'star killer story', I can't say for sure who the main character is. It could be someone named 'Star Killer' if that's the title of a character in the story.
A powerful and evil dragon could be the main antagonist. This dragon might have a grudge against the dragon slayers in general and specifically targets Lucy because of her growing reputation as a star dragon slayer.
The main character is Thrawn, of course.
The main character in the 'Star Child Birthday Story' should be the 'Star Child'. This character is probably at the center of the story, especially since it's their birthday that the story may revolve around. Maybe this 'Star Child' has unique characteristics that make them different from other children, and these traits are highlighted during the birthday story.
The main character is Calrissian, of course.
The main character in the 'Star Dreamer Grace Story' is most likely Grace.
It could be a brand - new character that we haven't met before. Maybe a young Force - sensitive person from a remote planet.
A Mandalorian could be the main character. Mandalorians have a rich culture and history in Star Wars. A story about a Mandalorian who has to break from their traditional ways to save the galaxy from a new threat, like a powerful Sith Lord or a dangerous alien race, would be exciting. They could use their unique combat skills and armor to fight against the odds.