There are many posts here about dragging from Outlook to SharePoint. However, if you need to attach multiple files to send via email to external recipients (links are not an option, though dragging and dropping as links would also be useful in other scenarios), this can be really cumbersome with a large doc library, partly because you cannot select and then act on multiple items, except to download them as a .zip file, which are invariably blocked or stripped by AV software. It's a multistep process today at best.

Allowing drag-and-drop straight to an Outlook message would be a huge efficiency gain.