You need to copy a formula into several hundred or thousands of cells. However, autofilling with the mouse is a bit tedious. With this trick you can do it in a second.
But that’s only fun as long as it’s a few dozen cells at most. However, if it’s several hundred or thousands of cells, your mouse finger will fall off before you get to the bottom.
Solution: It’s so much easier, and it’s exactly the same whether it’s LibreOffice Calc or Microsoft Excel. Type the formula in the top cell. There can also be two formulas in adjacent cells. Select the cell(s) containing the formula. Again, the little green square in the lower right corner of the selected cell(s) comes into play: double click on that small green square, Excel automatically copies the formula to all cells below. It also stops at the bottom of your table or the sheet range used, as desired.
Alternative to faster horizontal fill: Copy the first cell with Ctrl+C (ctrl+C); those with the formula. Press Shift+Ctrl+right arrow (shift+ctrl+right arrow). This will mark all cells right to the end of the used range. Press Ctrl+V (ctrl+V), Excel pastes the copied formula.
(Original 06/04/2004, update with new Excel and LibreOffice version 10/28/2021)