Is there a way to make it ask the customer if they want to receive the online newsletter when they type in their email address for a receipt on the POS app? I don't create customer accounts for each order in store but most customers are happy to type in their email for a receipt. Seems time consuming and asking too much personal information before I even ring them up....
I found that if you add the items the customer wants to the cart in the POS app then go into the cart page you will see "Select Customer" under the products they are purchasing. Select the plus icon to the right then select the plus icon in the top right corner. You can then add their info before taking payment and ask if they want to be on the email list, there's an option for accepts marketing at the bottom. Hit save and you should be good to continue with checkout.
Hope this helps as I was searching for the same thing and then started messing with the app more and came to this work around. Haven't tested it yet but I will be soon.