Ahh, that's the flow I was looking for. Thank you so much.

@EvilElf: There's no way to replace a session in an existing tab. But you can just close the tab and open new one. Plus, by default, if you are closing the last (only) tab, WinSCP pops up Login dialog automatically (if you have disabled that, you can restore it in preferences). So if you work with one tab only, the "Disconnect" command actually does what you want.

(What @eddiek wrote is not correct)

Try this:

Go to - Options > Preferences and then Environment > Explorer. Look for this option under Miscellaneous
'Open new externally initiated sessions in existing window'

@eddiek: This is not working for me. Maybe there is a setting causing the behavior? I can right-click on the tab, or click Tabs from the menu, then Sites. Both exhibit the same result; a new tab.

Tabs > Sites > (select your site). This will open a site connection within the same current window and the previous connection will disconnect.

Is it possible to connect to a new remote site WITHOUT opening a new tab? I can't seem to find a topic asking this, or a setting.