Here are two examples of copying using the buttons.
Here is copying using the keyboard shortcut keys, which appear in a different color on each button.
Here is an example of copying a contraption that uses rekindle, a feature that will duplicate a part of your contraption at the timing that you choose (here, the contraption regenerates a leg every 10 degrees of rotation).
Here is another fast copy -- using "C" for copy, and the arrow keys to move the copy over and down. Once I finish a row, I press SA, for Select All, then continue pressing C, and using the keys to move it down and lower.