Thanks for your report.
I will take a look at this issue.
The new beta has a feature covered in Tracker Bug 760:
"Remember the last selected stored session on the Login dialog".
This is a nice addition, but I found that there's a small visual problem when the name of the session is wider than the available space of the containing window. The focus goes to that element and scrolls to the right so the folders aren't visible anymore. This doesn't happen if the name of the last used session is smaller than the available width.
Would it be possible to make the window of the login dialog resizable (so that the resizing changes the width of the right inner box where the sessions are displayed)?
If that would be possible and WinSCP also stored the last size of the window then we could widen the window to the width of the widest entry and this effect above wouldn't occur anymore.
Apart from that scrolling bug, a resizable window would be nice anyway :-)