I find a way to import multiple RIS files from downloads folder. I am using EndoNote X7.7.1 on mac OS 10.12.6. Right click on RIS file and select EndNote X7 as default application to open RIS format. Then you can select any number of RIS files at once and double click, boom EndNote imports one-by-one. The one drawback with this is all the files go into main folder on EndNote and you have to move them into customized groups, if you have any.