Custom Button URL in Automated Emails

Site URL: https://blue-mandolin-zhxk.squarespace.com/config/commerce/customer-notifications/customer-engagement#product-review

I would like to change the URL for the "Leave a Review" button in Customer Notifications, to redirect to a different review site. I know I can create a new email with the correct link, but this automation times the email to send 14 days after a purchase- I'd like to use this feature so customers get the email at this specific time. I've tried adding a link manually (it doesn't let you add a button) and then deleting the Review button, but the delete option is greyed out. 

Thanks for your help!!

Carina