diff --git a/README.Rmd b/README.Rmd
index 3a34e5a..2ee1375 100644
--- a/README.Rmd
+++ b/README.Rmd
@@ -156,7 +156,7 @@
 
 ## Overview Slides
 
-Like in the old Google-Docs-based slide workflow, a slide titled "Overview" or "Überblick" is automatically turned into a table of contents: its body content is replaced with a hierarchical list of all `#` and `##` slide headings, and each entry links to the corresponding slide.
+Like in the old Google-Docs-based slide workflow, a slide titled "Overview" or "Überblick" is automatically turned into a table of contents: its body content is replaced with a list of all `#` chapter headings, and each entry links to the corresponding slide.
 
 ``` markdown
 ## Overview
@@ -164,6 +164,12 @@
 (any placeholder content -- replaced automatically)
 ```
 
+To also include the `##` sub-headings below their chapters, add `{data-overview-subheadings=true}` to the heading; the list is then laid out in two columns:
+
+``` markdown
+## Overview {data-overview-subheadings=true}
+```
+
 The TOC is generated when the presentation is opened, so it always reflects the deck it is part of. Slides without a heading and the title slide are left out.
 
 ## Incremental Bullets