On overwrite confirmation prompt, you have option "Append". If you select it and the source file is larger then target file, you will have two options, either to append whole file to the end of the target file or to resume the transfer (this is what you want). The function is available only with SFTP protocol, not with SCP.

Hi,

How do I make WinSCP think that a file is a broken download, when in fact it was downloaded completely? The reason I want to do this is that I use WinSCP to get a web server log, and since it only grows by getting new lines added to its end it would be nice if I didn't have to keep downloading the whole thing (especially since I'm on a modem, grr), but just the lines at the end that have been added since I last logged on.

Thanks!