I'd call it more of an effective definition, because the marginal note, which identifies the content of a provision for awareness reasons and for being able to identify what's in a provision.... You're right that it wouldn't have force of law, but it certainly labels the provision. The marginal note is “Femicide...and other aggravated circumstances”.
This means that when a female is killed in any of the (a), (b), (c) or (d) circumstances as I've described them, the legislation would define those circumstances as femicide.
That is my understanding of the effect of the provision.