How to save multiple array in Settings Api single section

If I am not mistaken, the settings api only storing one single data array in wp_options table . You can only change the field data in the section array.

But what if I need to add a dynamic data in the same section array?

For example:
Let say I got multiple users in my site, and I need to set their membership expired data based on each user roles by a plugin.
In the plugin, I would like to store each of the roles with the expiry date by using settings api. And it would be:

Subscriber => 30 days after registration
Contributor => 60 days after registration
Author => 90 days after registration
Editor => 120 days after registration
…etc
each role will be store in single array. and all these array will be store in single row in wp_options table like this:

array(
'Subscriber' = array(
        'date'=> '30',
         ),
'Contributor' = array(
        'cpt'=> '60',
    ),.....etc
)

Also I would like to edit/delete/add each of the role expiry date any time I want. I might have new custom role in the future, so it is essential the plugin able to add new rule for new role.

What I found on goolge are only tutorial on how to store the data in single array, but I did see some plugin done this, but just couldn’t understand how they done it with my current of programming level.

I don’t want to create another custom table,since the data that I want to store is not so much. The settings api seem fit my need in this situation.

Any guides or advice will be appreciated.