I just discovered that when I’m dragging a file from one folder to another, and the target folder contains subdirectories, If I leave the mouse pointer over the target folder for about three seconds, the target expands!
e.g. I have c:pers
Within that you’ll find c:persaccounts, c:persletters and so on.
In the Left-hand panel of Windows explorer, the folder c:Pers appears with a Plus sign.
Holding a dragged file over the plus signs for 3 seconds causes the folder to open.
OK, so you all already knew that. Sigh. It’s a new trick for ME!