@slestak: I was considering this an edge case.
Anyway, I have added this issue to the tracker:
Issue 2359 – Make option not to remember monitor configurable in GUI
You can vote for it there.

I wonder why this is not a setting accessible in the UI?

It worked! Thank you!!

You can create a custom desktop short to start WinSCP with the following commandline argument:

See also Why is WinSCP window not showing after I start the program? Only a taskbar button appears.

Good day comrades! I am running WinSCP on 2 devices. My home PC, and also my office PC. I have 2 monitors at home and also at office. I am sharing the INI configuration file between devices using OneDrive. The problem is if I worked with WinSCP yesterday at office, and today I open WinSCP at home, main window is opened on wrong monitor. And vice versa. Can I force WinSCP always open on primary monitor? Do not remember window position or something. Thank you