Chibis traits are a world of mystery. Most explain themselves.
Some are a secret, a mystery trait.
All of them do have impact on certain parts of the game.
As time goes by so will our documentation become more comprehensive.
Until then, find the rarest trait and try to fuse with that Chibi to receive that trait.
Just keep in mind, only trait 1 and trait 2 can be inherited. Trait 3 can never be inherited. The fusion lab list won't even show trait 3, so no worries in accidentally fusing with it.