diff --git a/website/docs/sidebar.md b/website/docs/sidebar.md
index bbc1aadefa..1978b05e2c 100644
--- a/website/docs/sidebar.md
+++ b/website/docs/sidebar.md
@@ -227,3 +227,18 @@ module.exports = {
   },
 };
 ```
+
+### Collapsible categories
+
+For sites with a sizable amount of content, we support the option to expand/collapse a category to toggle the display of its contents. Categories are collapsible by default. If you want them to be always expanded, set `themeConfig.sidebarCollapsible` to `false`:
+
+```js {5}
+// docusaurus.config.js
+module.exports = {
+  ...
+  themeConfig: {
+    sidebarCollapsible: false,
+    ...
+  },
+}
+```