When you are adding subscribers from an external form, you can also add extra attributes by using a specific input name pattern attributes['name-of-your-new-attribute']. This is what that looks like for storing a user's job.
To make this work, you also have to make sure job is defined as an allowed extra field on your email list's field allowed_form_extra_attributes.
Here are examples of methods to work with those extra attributes.
$subscriber = $subscription->subscriber;// get all extra attributes$subscriber->extra_attributes->all(); // return an array with all extra attributes;// updating an extra attibute$subscriber->extra_attributes->first_name ='Other name';$subscriber->save();// replacing all extra attributes in one go$subscriber->extra_attributes = ['first_name'=>'Jane', 'last_name'=>'Dane'];$subscriber->save();// returns all models with a first_name set to John$subscriber->withExtraAttributes(['first_name'=>'John'])->get();