Courier's Lists API allows you to create lists, subscribe recipient profiles to them, and notify every user on the list with a single Send API call, reducing the need for multiple API calls triggered by the same event. With this feature, you can easily reach users in shared workspaces, notify followers of specific projects, or send notifications to users who opted-in to select notifications. The Lists API also supports wildcard sends, allowing you to notify subscribed users across multiple lists with a single API call. This enables flexibility in creating lists for various use cases and sending notifications to users with matching subscriptions.