Connect to remote site, double-click somefile.php or similar to edit it, file gets downloaded, opened, fine.
Now switch to some other app or main WinSCP Window with Alt-Tab.
Then try to get to the editor-window again by clicking it in the taskbar, you can't. It always brings the main WinSCP to front.
Workaround 1: After Editor in Taskbar you have to click main app in Taskbar then it shows Editor
Workaround 2: With right mousebutton use "Minimize" in Taskbar on Editor Window, then it will show up, if you click it again.