When I upgraded to Windows 10 I lost the multiple docs upload feature in Sharepoint. How do I get it back? I've never been able to access it in Firefox or Chrome, but I could in IE. But now even in IE it's single upload only. Sometimes when I click on the upload link I see the multiple docs feature for a split second but then it goes away. Any ideas?

Hi Ratel, multiple upload is not supported in Chrome / Firefox, and it is not working on Edge browser too.

I just did a quick test, it works on Internet explorer (make sure you use Internet Explorer), through drag-and-drop.

Once you drop it, your document will starts uploading.