There is no option to control it, this feature is always on. testing it here, the files or folders are added to the playlist when dragged from Windows Explorer. Honestly, I'm not sure why it doesn't work for you. One of the possible reasons is that antivirus or any other sort or protection software blocks this operation.It is the Standard Windows Explorer... before the Update it was possible and by all my colleagues it is possible too... is there any setting in the RB?
We can't reproduce the issue here, drag-n-drop works properly. In some older versions, you can drag to any place in RadioBOSS window, starting with v5 you need to drag onto the playlist.This latest update has broken the ability to do this.