Select a cell (or a range of cells). Rest the mouse over the highlighted border. Click and try to drag the cell to a new place. 24 out of 25 times a new range of cells is selected. Occasionally the cell is dragged. The feature is allegedly there but it doesn't work consistently - hardly at all in fact. In Excel, the pointer icon changes when you mouse over the border. This tells you that if you click you will be able to move. There is no such change in Calc, which can make it very frustrating as you continually try an click on different parts of the range to hopefully try and get the right place.
We don't support this feature when you click on the border. In calc you have to select a cell range and then press the mouse button !in! this range and move the range. There are some ideas to support selecting ranges at the border but nothing has been done in this direction yet.