A workaround however (even if not ideal) would be to create a collection with one item with a file attachment field.
This way you could use a collection list in your slide to display the link and therefore download the schedule.
Your client can access the Schedule collection inside of the CMS and change the attachment of the collection item.
The downside of it is that it will create a collection page template but you can quickly design a page template dedicated to download it (just in case someone put the direct url in his browser) or setup some redirection or even “do nothing” as I think if you don’t put any element on a collection page template webflow will reference it as a 404.
But at least for your client you will get what you need.