Hi Carson,
This line of code is where you get the user_list_id created in this example. However, if you are using an existing user_list_id you don’t need to create it and you wouldn’t want to pass in the user_list_id into the id field in this line of code. You actually would need to pass in the existing user_list_id in this line instead. As for the other question, hashing would be a good way to protect customer’s privacy so the customer data must be normalized and hashed. It is the same for the Google Ads UI that these sensitive information would be hashed but we don’t directly see the change as it’s something working underneath the hood.
Thanks and regards,
Xiaoming, Google Ads API Team