How does the customer portal login work with passwordless login enabled?
When passwordless login is enabled, customers do not need to create an account. They can click a manage subscription link on your storefront, which takes them to a page where they can enter their email address. Bold then sends that customer an email that contains a one-time link to the customer portal page where they can manage their subscription. This link expires after 15 minutes.
Read more about this in Passwordless Login in Subscriptions for Shopify Checkout: https://support.boldcommerce.com/hc/en-us/articles/18672947452948-Passwordless-Login-in-Subscriptions-for-Shopify-Checkout