From the Person config page one can Allow To Login, which leads on to the Create User workflow.
This request is to add the option to select an existing User and make the connection between the existing user and the person.
Why? Because for new HA adopters, it isn’t obvious that one creation sequence makes any more sense than the other.
As discussed in #frontend channel on discord.
I created my children as people who are tracked via asuswrt detecting their phones, and as users who have the smartphone app on the same phones. The thing that is not quite intuitive is that the concepts “user” and “person” are similar and yet not interchangeable, and cannot be linked if created in the wrong sequence. It’s not the end of the world but it certainly is not obvious, especially as one sets up these basics as part of onboarding and therefore during the first engagement with the product when most error prone. It would be nicer if one could refer to an existing user from the person screen, as part of the “allow to login”, as well as create a new user.
Reasonable advice in the support channel:
“… not all people are users, but all users are people. If you want a user, create the user and it will create the person.”
Or
"Simply go into your person and check the login option. "
Ideally, one should be able to create users and people in any order, including in parallel, and still link one to the other.
You are absolutely right. It is not well designed and awkward to understand the strange logic. I had to change ownership and reassociate some people to users and in order to do it I had to work with the .storage/.auth file, many restarts and deletes and recreation of users starting from people in order to respect the workflow and have people-users linked correctly.
2022.2 was the “streamline” HA version: this section surely needs to be streamlined. 
So far this has worked for me:
As I said. This has work so far. I’ll edit this if it breaks