With the Orocrm Subtemplate inside email extension, you can enhance the default functionality of OroCRM email templates.
Subtemplate allows you to leverage the relation of one to many.
For example, a customer has placed an order but also has an abandoned shopping cart. With Subtemplate you are able to combine two email templates in one and display both the invoice and a reminder to recover the abandoned shopping cart.
Demo video: https://www.youtube.com/watch?v=GJ3PzYcwhnk