You can manage customers in bulk using CSV export/import:
Export: Download your customer list to work with it in tools like Excel or Google Sheets.
Import: Bring in customers from an existing list using one of these import types:
Automatically subscribe (optional): Enable Automatically Subscribe during import to add imported customers to your mailing list. If you don’t enable it, customers won’t be subscribed automatically (you’ll need to enable it later manually, or they can subscribe themselves from the Client Zone if available).
CSV requirements: