The current stable version has an option Keep main window open when the last session is closed :
https://winscp.net/eng/docs/ui_pref_window

WinSCP 5.16 (currently beta/RC) does not even close tabs of sessions that are not re-connected.

I've found that when I sftp somewhere and connection gets lost, and I say not to reconnect, winscp closes. I'd like to see it stay open unless explicitly closed by, file..exit. Otherwise, it kind of gets teadious to go: start...programs...winscp...winscp, everytime I get disconnected, or can't reconnect for a short period of time.

I'm sorry if this has been discussed previously, I couldn't find it if it was...
Thanks.