Add Granular content to email layout

Hi,

From https://customer.io/docs/journeys/3-layouts-and-customerio/ it seems like the only way to add content to a layout is using {{content}}.

However, I have an usecase where I want to insert a particular text before an image and particular text after an image. 

The image is part of the email layout which is static, however the contents can vary. In other words, I want to do something like this:

{{content_before}}

<yield to template layout>

{{content_after}}

How do I do this?

Thanks,

Mayuresh