I opened a PMR last week asking IBM why drag and drop a file to a folder is not working when i use Windows Explorer.
Bellow the answer.
The MS desktop plugins do not currently support dragging directly to a folder. Files must first be created on the server (by adding to Files) and then they can be added to folders. Connections folders are not containers – they are collections of files that live elsewhere.
Already logged as a story for future consideration: MS Desktop: Ability to DND a file directly to a personal/community folder (LC 112847)