We should be able to do it with custom attributes.
The correct syntax for download is:
<a href="path/file.jpg" download="Picture of an elephant">Download the picture of an elephant</a>
So it’s exactly a custom attribute. But the Download name is reserved by Webflow.
http://vincent.polenordstudio.fr/snap/u9koc.jpg
So, you can use a custom code element to address that. It works with CMS. As soon as you have a custom code element inside a dynamic list, you can inject some of you CMS data into the code. Here you’d possibly need to retrieve the URL of the file and the description of the download.
Select the URL, then the description, and click +Add field on the top right corner to link that portion of code to your database.