Here’s the URL to the built-in document set downloader page: {SiteUrl}/_layouts/DocSetExport.aspx?List={ListId}&ID={ItemId}. It takes in the GUID of the list and the ID of the document set. Here’s an example: http://sharepoint2010/sites/docman/_layouts/DocSetExport.aspx?List={4E2D11F5-7500-476A-B001-62A7BF92FD50}&ID=10 Adding a Custom Action to the Document Set List Item Menu using SharePoint Designer To add a custom action, open the site in SharePoint Designer and navigate to the document set list. Add a new list item menu custom action: Provide a Name, Description, and Navigate to URL: Save the custom action, and test it: I want to mention that there is a drawback to this approach. The custom action will show up for every list item, not just the document set. The list item menu will appear on documents in the document set as well: Adding a Custom Action to the Document Set Ribbon using SharePoint Designer We can also use SharePoint Designer to add a button ...