Although this menu option is on the top level window, it is generally for the Grid (Table) panels.
Copy, Paste, Clear
To use these options, first you need to highlight cells (by left-clicking on the mouse, and hold it or hold 'shift' key and left-click again).
*The 'Copy' and 'Paste' icons are also accessible from the toolbar and a key-combination 'Ctrl-C' and 'Ctrl-V' can be used for copying and pasting respectively.
**Note that only one whole column (or row) can be selcted by clicking the label.
These Edit menu items are enabled when a whole column/row is selected in the Grid panel.