There's no way to hide the columns. Maybe you have resized them to a zero width. Place your mouse cursor just behind the column separator line on place of the invisible column. The cursor should change. Then drag to the right to reveal the column.
I have the same problem. The horizontal scroll bar is huge, and I only see strange artifacts in the column headings bar to the right of the Destination. If I could find the separator line, I could double-click it, but I think there's something fundamentally broken.
Can you send me an email, so I can send you back a debug version of WinSCP to track the problem? Please include a link back to this topic in your email. Also note in this topic that you have sent the email. Thanks.