Copy an object
To activate " Copy " mode, click the " Copy " button.
Your cursor will turn green. You can then click on an object you want to copy. A copy of that object will be attached to your cursor.
You can then paste this copy as many times as needed with the left click of the mouse.
Delete an object
To activate " Deletion " mode, click the " Delete " button.
Your cursor will turn red. You can then click on the objects you want to delete.