Thread:Skin talk:Vector/Collapsible Sidebar navigation

I am migrating my wiki to a new version. (1.19.1 to 1.24.1) After many attempts to get the Vector extension installed I read that it's been discontinued for newer versions and integrated into the core of the Vector skin.

Unfortunately it appears that the syntax to get a collapsible sidebar navigation has changed.

Modifications to MediaWiki:Sidebar don't have the affect they did before and I no longer find an option for "Enable collapsing of items in the sidebar in Vector skin".

Has this feature been removed or modified?