This is a feature request,
I have been a long and very loyal user of xfce but since MS Windows 7 I was missing some more interactivity when copying things from one place to another.
When I copy something and on the half way of the process, I realize that I need to add something to the copy process. 
It would be nice if the dev-team could add some kind of "copy-queue-list" so that you can add or remove while the queue is being processed.
Another feature that would be really great is to give the user to pause and continue the copying process.