These are the first two countries that appear in the SMS dropdown by default. If none are selected, they will automatically be set to US and UK.
Having this tick box selected will present a button on your product page instead of an integrated notification subscription form. Clicking this button will trigger a pop-up with the subscription form. Also selecting the ‘trigger pop-up widget automatically’ tick box will launch the widget as soon as someone visits the product page.
Selecting this tick box means that customers must also agree to receive marketing emails or SMS from you in the future in order to subscribe for a back in stock notification.
This is the polaris color picker for the Now Back in Stock popup buttons.
This is the subject line that will appear when the email is sent to customers. Inputting the placeholders {{product_title}} and {{shop_name}} will automatically populate these fields with the relevant product title and the shop name respectively.