Inserts the sum of a cell range into the current cell, or inserts sum values into selected cells. Click in a cell, click this icon and optionally adjust the cell range. Or select some cells into which the sum values will be inserted, then click the icon.
LibreOffice automatically suggests a cell range, provided that the spreadsheet contains data. If the cell range already contains a sum function, you can combine it with the new one to yield the total sum of the range. If the range contains filters, the Subtotal function is inserted instead of the Sum function.
Click the Accept icon (green tick mark) to use the formula displayed in the input line.