Parenthood: Need help ending a childhood phase

Update: I finally played again today and tried the Sim Info mod on my picky eater child. Turns out the name of the trait hasn't changed, it's still the picky eater phase, and now I even know the letter: D. But that doesn't help me, as the phase still doesn't end and the cheat still doesn't work.

I guess there is no solution then. Never mind.