How do I show a list of links to the other items in a collection on a collection item page?

Site URL: https://clementine-tarpon-j5as.squarespace.com/module-1/module-1-2-more-stuff

I'm trying to make a custom collection of learning modules, and for each lesson in a module (the equivalent of a blog post in a blog collection), I would like to show a list of navigation links to the other lessons in that module.  I've got my module.list and module.item pages for the collection. {.repeated section items} works when I run it module.list, but when I run it in module.item, nothing shows up.

How do I access the other items in the collection from within an .item page? 

The blog page in my template has previous and next buttons on each blog post page, so I think it must be possible, but I don't have access to its code under the hood since it's using the squarespace default blog.