Why doesn't usual Drag&Drop work in Windows 10?

Solution 1:

You see a effect of the User Account Control. Drag & Drop only works for programs that have the same permission level. If you run an application as admin, you can only drag and drop files from applications that also run as admin.

User Interface Privilege Isolation (UIPI)

UIPI blocks Windows messages being sent from process with a lower MIC level to one running at a higher MIC level. Drag-and-drop is implemented via Windows messages. Therefore, if you try and drag-and-drop a file from Windows Explorer (medium MIC) to Notepad running elevated (high MIC), the Windows messages are blocked and drag-and-drop doesn’t work.

Moving the slider down to the lowest position no longer disables UAC since Windows 8, because UAC is required to use the store apps, because UAC provides the sandbox in which the apps run isolated.

The version 8 is very old, so Windows detects that it has issues running under normal user permissions and requires admin rights.

As mentioned above this is a feature that can't be fixed. But there is a workaround to run Explorer as admin to be able to drag & drop files from Explorer to a process running as admin.

Solution 2:

I have this exact same issue with an older version of Wavelab and my only workaround is to drag and drop onto the Wavelab desktop icon shortcut. For some reason this opens the file in the program as normal and can also be used to add more files into it while running.