You can add connector lines and other drawing objects only to a chart. You cannot add them to the datasheet.
Connection sites appear as blue squares.
Locked connector ends appear as red squares. Locked connector lines move with the objects they connect. Unlocked connector ends appear as green squares.
To move the connector line, drag one of its ends, and connect it to another site or object. To detach the entire line, drag its middle. If the connector line has a yellow adjustment handle, dragging the handle will change the shape of the connector line, but not detach it.
Locked connector line
Unlocked connector line