
(note that the destination is "Custom Path > .." and the target DSN is ".")
Next, navigate to the desired destination:

click "Save" and the response is

Circumvention:
At the initial display (above), click on "Home" in the upper-left (or any valid destination), and receive

Navigate to the desired destination, and provide an alternate filename, if desired:

click "Save", and the whitelist is correctly exported.
(Take note that under Windows, the initial export panel correctly anchors to "My Documents" (Windows/XP).)
Possible origin of the problem is anchoring (the "Custom Path > ..) to the Linux root /Home directory, rather than the users true Home. NoScript, running under the user, would not normally have write access to the root directory, nor the root/Home anchor.