Subscription Customers are tagged in Shopify as "Manage Comics - Active"
Find all Active Subscribers
To search for subscription customers, in Shopify go to Customers, click on Tagged With, then enter customer_tags CONTAINS and select "Manage Comics - Active".
Create an email list for subscribers only
1 - Save the segment.
2 - Name the segment.
Note: You can only send emails to customers who are "Opted In" to email.