(we are the one's that brought this up...)
The Ctr-Shift during drag works on Windows 7 for us, but not on our Win 10 boxes (several different major builds.)
It appears the desktop is not responding properly to the mouse over as I think it is responsible for sending the message that a drag is over the window.
I have a desktop WinForm app that accepts drag/drop from Explorer (including desktop) but it doesn't allow the the drop for LF. In my app, running on Windows 7, the DragEnter is looking for the `FileDrop` format.
Here is the list of formats on the clipboard from on Windows 7:
EXPLORER:
Shell IDList Array, DragImageBits, DragContext, DragSourceHelperFlags, InShellDragLoop, `FileDrop`, FileNameW, FileName, IsShowingLayered, DragWindow, DropDescription, DisableDragText, IsShowingText
LF CLIENT :
FileGroupDescriptorW, FileGroupDescriptor, FileContents, `LFObjectOrPage`, System.String, UnicodeText, Text, DragImageBits, DragContext
For the client drop the string formats contain the filename. I can't see into the objects as I don't have the SDK.
So, a guess is the File Explorer on our Win 10 boxes is missing an extension that allows the processing of objects drag/drop from LF.
I'll try the drop test on Windows 10 tomorrow.