“ClosingActions” option for FrontEndAttachCell

I'm looking to find the possible values for the ClosingActions options FrontEndAttachCell. I have found SelectionDeparture and ParentChanged` so far.

Moreover, is there a general method to determine the options for "undocumented" functions such as this one?

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Unfortunately, the best "general method" I know of is to ask the question here and hope that someone with source code access replies. John Fultz has helped with a lot of undocumented front end functions in the past, so I think you stand a good chance. –  Oleksandr R. Dec 10 '13 at 19:14