I do not think this is widespread problem. You seem to be using niche WinSCP feature (workspace shortcut) for years, although you do not really want to use it.
So do not use it. Use WinSCP application shortcut.

That sounds plausible. Might be worth adding to the documentation somewhere. Perhaps a troubleshooting or FAQ page?

I do not think this has anything to do with any upgrade.
It's only about your configuration and your workspace.
If I remember correctly our previous lengthy discussion, you are not starting WinSCP with an application shortcut. But probably with a workspace shortcut. And if you didn't have any session opened when closing WinSCP the last time, the workspace shortcut will open WinSCP in the same state.

OK, I think I finally stumbled across the Open Sesame command, through pure dumb luck. I finally tried Tabs-Close Tab. When I closed and re-opened WinSCP, the remote site was automatically connected and displayed in the right side panel.

Maybe it’s just me, but I find the WinSCP interface incredibly confusing. At the very least, this technique needs to be much better documented. Perhaps a “Common Problems” Web page is in order, explaining how to resolve this issue.

I still don’t understand why this problem occurred when I merely upgraded to a new version. The show Login dialog on startup and when the last session is closed was always/still checked, so that wasn't the cause of of the problem. That makes me worry this is going to recur every time I upgrade.

I’m sorry if I sound obtuse, but I’ve spent an hour going through all the dialogs and menus I can find, and I still don’t see how to make WinSCP to automatically connect to the remote site upon startup. I can’t find the “Interface\AutoStart Session” option you mentioned.

The “show Login dialog on startup and when the last session is closed” is checked, but a login dialog never appears: Once I enter the master password, the commander interface opens, with two local panels showing.

I launch WinSCP via an task bar shortcut. I re-read my old post again, and cannot tell (and don’t remember) what I did to finally make it work. Is there a FAQ or troubleshooting page that explains how to resolve this issue? I’m desperate to make this work.

Didn't we had lengthy discussion about this already?
Commander interface: Remote site not in right panel on startup

I just upgraded to WinSCP 6.3.1, and am having the same problem I encountered during the previous upgrade: The remote site no longer shows in the right panel of the workspace. This automatic display of the remote site was working fine until I did the upgrade this morning, but as soon as I launched WinSCP after the upgrade, the problem appeared.

When my mouse hovers over the workspace tab, a tooltip opens and shows the correct user name & IP address, but says the remote site is “disconnected.” Clicking the workspace tab connects to the remote site and then displays it, but why isn't it doing that automatically when I launch WinSCP?

Just as important, how to prevent this problem on the next WinSCP upgrade?

I’m running Windows 10.