Custom deck/subheading for newsletter?

Hello.

In Substack, you have the option to create a custom subheading/“deck” for your posts.

This is great for the preview on various social media sites, but it’s arguably even better for the inbox. The subheading is the little bit of text that shows after the subject line.

How do we adjust this on Ghost? I don’t see an option anywhere in the text editor like there is on Substack.

Thanks.

Many themes show the excerpt (which is customizable in the right side menu of the posts menu) below the title. And it looks like it’s getting included in the newsletter, too, because here’s my latest missive:

In my gmail inbox:

On my site:

Looking at what gmail’s showing, I’m thinking I should set longer excerpts…