Line breaks in data in front matter of markdown file

[chmgui]

Hi All
Newbie here. Does anybody know how to include line breaks in the data of a variable in the Front Matter of a markdown file?
I tried the Indent Code Block in this link https://www.11ty.dev/docs/languages/markdown/ and it didn't work.
Tried using a vertical | as per this link https://discourse.getgrav.org/t/multi-line-strings-in-frontmatter/1226/5 and it also didn't work.
https://stackoverflow.com/questions/3790454/how-do-i-break-a-string-in-yaml-over-multiple-lines

Thank you very much

[pdehaan]

This worked locally for me

---
title: HOME
eleventyComputed:
  excerpt: |
    ## {{ title }} subheading

    This is some content.
    Linebreaks?

    Or multi-blank lines for a line break?
author: pdehaan
---

# {{ title }}

{{ excerpt }}

Which generated the following output:

<h1>HOME</h1>
<h2>HOME subheading</h2>
<p>This is some content.
Linebreaks?</p>
<p>Or multi-blank lines for a line break?</p>

---

UPDATE: Pushed my demo to https://github.com/pdehaan/11ty-1573-frontmatter-multiline

[chmgui]

Thank you pdehaan.
Okay it is not working because I am using the variable in a Nunjucks njk file. My apologies for not being clear.
How to get it to work in .njk file ....
node --version
v15.5.0
npm --version
7.3.0
$ npx @11ty/eleventy --version
0.11.1

UPDATE - found the solution - {{ service.data.description | striptags(true) | escape | nl2br }}
https://mozilla.github.io/nunjucks/templating.html#striptags-value-preserve_linebreaks

Thank you once again Peter!

[pdehaan]

Ah sorry, I misunderstood. I thought you were using a .md file w/ frontmatter.

If you're using Nunjucks/Liquid, you'll need to create a Markdown filter or paired tag to convert the frontmatter markdown string (since Nunjucks/Liquid won't run output through a markdown parser). I updated https://github.com/pdehaan/11ty-1573-frontmatter-multiline/blob/master/src/nunjucks.njk and added a "markdown" filter to the .eleventy.js config file. And if you want to do a paired shortcode instead (ie: {% markdown %}{{ excerpt }}{% endmarkdown %}), there should be an example in #658.

But yeah, if you only want to handle plain text w/ line breaks without markdown formatting, I think your solution of nl2br is way better. 👍