On the standard toolbar, click "customizing local layout" (beside the question mark button) or press Alt+F12. Then
select "Quick cut and paste". With this feature, you can copy texts by just highlighting it using the mouse. To copy, right-click on the start of the text to be copied and hold until the end of the text to be copied and then release. To paste anything from the clipboard, just right-click with the mouse. For 4.6C, this won't work on ABAP source code area. This is very useful when copying data from one field to another, etc.