How to send an approval email to customers via the Shopify app?

We are a wholesale company so when we have a new customer sign up to the site, we tag them as a ‘wholesale’ customer so then they can view all our products and prices.

This is very simple to do online, we simply just click the email address in the Customer Overview and can preview the email before we send it (which alerts them that they have been approved to the site). However, we’re struggling to find out how to send the same email via the app? The tagging process is the same but when I click on the email in the Customer Overview, it just takes me to a blank email rather than having the default message there that we have created.

Please can you advise us on how to send the same approval email through the app? Many thanks.