Allow members to manage newsletters without Portal

Hello, I am not using Portal as my member-management tool.

I am trying to implement a solution in the account page where my members can toggle ON and OFF the newsletters they want to subscribe. For instance: I have 3 newsletters: A, B, C. I want to make sure that in their account page they can manage the subscriptions of individual newsletters, in case they want to only receive A, or want to only unsubscribe B.

I know for sure this can be done using Portal (which I am not, I am going full customization), under manage newsletters.

But this is not mapped in the members documentation.

Does anyone know how to help in this?