So. Self resolved after reading the wiki many times. To be honest, the wiki text is "sub optimal". (Trying to be generous with my description).

Having re read it, and found the answer, it is not intuitive to put account details for a payment processor in a user profile - especially for someone migrating from the previous platform where these details were together with the on/off button for each payment processor. Now I get it that you want multiple payment profiles for multiple sellers, but I was not expecting that for the main payment profile. Being a wiki, I looked for the edit button to improve the details, but no edit button.