Not sure about Windows 10, but you could try the following which seems like it might work from testing on Windows 8.1.
Open the windows task manager, I think on windows 10 you then need to select view details.
Right click on the calc application in task manager and select maximize. You might need to expand the LibreOffice application group to see calc.
Using the mouse, select the top bar of the window and drag down away from top of screen. This should switch back to the tall window but with the top edge visible in your display.
Use the mouse to select the top edge of the window and drag down to reduce the height of the window.
Select the top bar of the window and move the window higher on your display.
Repeat the last two steps until you can see both the top and bottom of the calc window, then you can adjust to size and shape that suits you.
Repeat the last two steps