By default WinSCP should allow and understand both slash types, even mixed. This means that you could add a windows folder path to a current selected path in WinSCP without worrying.
I think this is essential to allow WinSCP to be truly native on Windows.
Tried to add this to tracker but for some reason the login to tracker will not work any more. Tried the forum password and my bugzilla username/pass but neither work, so I have raised it here instead.