Could you add some clarification re: wedding bells, baseball cap, tennis racquet, door knob, golf club, soccer ball, soccer field, sunglasses, Christmas tree, water tank, bus stop, fire truck, etc.
By your lesson, these should all be “à” (what something is designed for), but in fact this whole genre is “de”.
Specifically, why is it “boîte à bijoux” and not “boîte de bijoux” ? Other than convention.
Clearly, these are not just a few exceptions, but an entire class of compound nouns (open form, noun+noun) that is not covered in the lesson.