How do I change a PDF dictionary key using CosEdit?

Q: How do I change a PDF dictionary key using CosEdit?

What I do is I find where I want to add a new key. In specific, I'm
trying to add the key 'NumCopies' in the ViewerPreferences dictionary
of a PDF file.

I right click in the appropiate dictionary, I click on New Atom ->
number. It adds the new key called 'New_Key_0' and I can manually
enter the value.

I need to change the 'New_Key_0' into 'NumCopies' and I cannot figure
out how to do that using your GUI. I looked in the help but could not
find this issue addressed.
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A: To change key name simply select the dictionary key, and then mouse
click once more. This is similar to how you would rename a filename in
Windows Explorer.