Dear jean-emmanuel, I've tried to recreate this behaviour to make a video screenshot, but I can't, so apparently it is either inconsistent or I likely don't understand the conditions to make it happen.
I usually use two monitors, but when I try to open the software only on my laptop without other monitos its main window seems to have memorized the position it had on the second screen, but it stays there as if there still was a second active monitor, and I can't move it to the only-active monitor, not even by using the windows "start+arrows" gestures.
Then, after attaching again the second monitor I can see again the main window sitting there, and it becomes accessible again.
Those - I was referring to them as "start+arrows" -don't work either.
The hidden OSC window doesn't react to any gesture. I can only see it's open and running because it's shown as such in the Windows toolbar, and in the small preview you see when you lay your mouse over the icon.
Select the program in the taskbar with the mouse.
You can tell whether a window is open by the small underline under the icon in the taskbar.
Windows logo key + Shift + Left arrow or Right arrow
or
Shift+Right-Click the taskbar button and choose the "Move" command from the context menu.
move it with the mouse or arrow keys (is a bit choppy).