Add cascade and param

docs/sources/write/front-matter/index.md

@@ -165,6 +165,20 @@ For example, `https://grafana.com/docs/writers-toolkit/`.
 
 For content reused in Grafana Cloud, prefer the open source documentation as the canonical page.
 
+### Cascade
+
+`cascade` is a map of front matter keys. The values are passed down from the parent to the page descendants.
+
+You can use `cascade` to define variables. For example:
+
+```
+cascade:
+  PRODUCT_VERSION: 10.1
+  PRODUCT_NAME: Grafana
+```
+
+Use the [param](https://grafana.com/docs/writers-toolkit/write/shortcodes#param) shortcode in the topic body text wherever you need to insert the variable.
+
 ### Date
 
 `date` describes the initial publish date of the page.

docs/sources/write/shortcodes/index.md

@@ -381,6 +381,43 @@ In this example, the image's display size is changed to have a maximum width of
 {{</* figure src="/static/img/docs/grafana-cloud/k8sPods.png" width="1275" height="738" max-width="500px" class="w-100p" link-class="w-fit mx-auto d-flex flex-direction-column" caption="Pod view in Grafana Kubernetes Monitoring" caption-align="center" */>}}
 ```
 
+
+<!-- vale Grafana.Spelling = NO -->
+
+## Param
+
+<!-- vale Grafana.Spelling = YES -->
+
+The `param` shortcode provides build-time variable substitution.
+
+To add a new variable definition:
+
+1. Define a [`cascade` variable](https://grafana.com/docs/writers-toolkit/write/front-matter/#cascade) in the parent topic.
+1. Insert the `param` variable where it's required in the parent and child topics.
+
+> **Note:** If you use the `param` shortcode in headings, you must use `%` in place of `<` and `>`. For example: `{{%/* param VARIABLE */%}}`.
+
+### Example
+
+The front matter definition for a product version:
+
+```markdown
+cascade:
+   PRODUCT_VERSION: 10.2
+```
+
+The `param` shortcode in the topic body text:
+
+```markdown
+Welcome to Grafana {{</* param PRODUCT_VERSION */>}}! Read on to learn about changes to dashboards and visualizations, data sources, security and authentication, and more.
+```
+
+The `param` shortcode in a topic heading:
+
+```markdown
+## What's new in Grafana {{%/* param PRODUCT_VERSION */%}}.
+```
+
 <!-- vale Grafana.Spelling = NO -->
 
 ## Relref