To copy any frame on your canvas, including a composite frame, select it.
Either use the keyboard Ctrl-C shortcut or click on the Menu Icon in the upper left corner and choose Copy.
To cut the selected item, use Ctrl-X or click on the Menu Icon in the upper left corner choose Cut.
To paste the last copied or cut item from your canvas, use Ctrl-V on your keyboard or click on the Menu Icon in the upper left corner choose Paste.
Paste multiple times to make multiple copies of the item.
To duplicate an item, copy it then paste it.
To delete an item from your canvas, select it and hit the Del key on your keyboard.
To undo the last changes made to your canvas, use Ctrl-Z on your keyboard or use the Undo option on the Menu Icon in the upper left corner.
To redo the step, use Ctrl-Y. Each time you Undo or Redo, your project moves back or forward one step.