how to "copy" a tab in split view

The problem I have is the following: I split my window vertially into two tab groups.  I have a file in the left group but not in the right group.  I want to make it appear in the right group as well, so that I can edit it in the left panel, while referring to another location of the same file in the right panel.  How do I do this?  If I right click the tab in the left panel, I only found "move to the opposite tab group" in the context menu.  Is there a way I can do "copy to the opposite group"?

I saw this feature mentioned back on 2003, hopefully it is available now?
see http://www.jetbrains.net/devnet/message/572374#572374
"7. It would also be nice to "copy" tab(s) to a different group, rather than just move them."