Nevermind, it was answered already:
https://winscp.net/forum/viewtopic.php?t=26284
https://winscp.net/forum/viewtopic.php?t=26284
DuplicateFile
to work:
# Test.txt and Test.Dir both exist.
# after already connecting, and having the WinSCP.Session object already in a variable
$WinSCPSession.DuplicateFile(
"/Test.txt", "/Test.Dir/Test.txt"
)
Exception calling "DuplicateFile" with "2" argument(s): "Operation not supported."