To copy a folder, simply select the folder and drag it to the folder list on the other side (other file
panel), dropping it on the destination folder.  When the folder is dropped, a popup menu will appear.  Simply select "Copy" from the menu.  A warning will be displayed prior to overwriting any existing files/folders.

Access: Select a folder in one session.  Then drag and drop on top of a folder in the other session.  Menu appears when the folder is dropped.