diff --git a/book/_toc.yml b/book/_toc.yml
index a97c215..176a0d9 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -89,6 +89,7 @@ parts:
       - file: external/sphinx-iframes/README.md
       - external: https://github.com/TeachBooks/Sphinx-Indexed-Definitions/blob/manual/README.md #BUMP
       - file: external/Sphinx-PRIME-applets/README.md
+      - external: https://github.com/TeachBooks/Sphinx-Dropdown-Toggle/blob/main/MANUAL.md
     - file: features/visuals.md
       sections:
       - file: external/Sphinx-Image-Inverter/README.md