If for some reason, your main calibre window has moved off the screen, there are a couple of ways to try moving it back. This assumes that calibre is running and you can see the calibre icon in the taskbar.
- Hold down the Shift key and right-click the app icon. You should see Move on the context menu. Click on move and then use the arrow keys to move the calibre window back onto the screen.
- Use Windows Snap Screen. Click on the app icon then press the Windows key and the right or left arrow key. This should move the calibre window to the right or left side of your screen.
- There are several other ways but I've found these two to be the most consistently useful.