Tldr: how do you modify a contact’s name?

I’ve been playing around with these signal names functionality. Adding a bunch of people via names rather than phone numbers.

I can’t seem to figure out how to change the name of the person, or add a note to the person, otherwise modify the contact in any way. So if a person names themselves a, and I talk to them, and then they rename themselves b. I have no way to know their name used to be a, or that I added them and talked to them as a. I only now see them as b.

Ideally I’d very much like to add notes, or modify the name of my contacts. For my own reference. IE Bob from the coffee shop etc etc