Offscreen Window - Move Back to Desktop

Which part?

Resetting folder views would be the easiest option though.

Using the tutorial below to reset folder views would be the easiest option though. Just be sure everything is closed before doing to make sure everything gets reset.

Folder View Settings - Reset All to Default

Ok, but this is going about it the hard way.

1. Connect a 2nd monitor to your computer if able to.
2. Open Screen resolution settings.
3. Like in the screenshot below, drag and drop the 2nd display's image around each side of your main display (original monitor) in the "Screen resolution" settings to see if the offscreen window shows up on the 2nd display when it's at one of the sides around the main display.
4. If the offscreen window shows up on the 2nd display, then you can drag the window back to show on your main display.

Other way to fix this problem?
I don't have 2nd monitor.

Did you already try this?

Offscreen Window - Move Back to Desktop

It's your choice, but I do guarantee that it's 100% safe to use. I never post anything that isn't.