RC3 -- Can generate custom themes off the default theme

Not sure if this is by design or if it is a bug. The Windows > Themes > “Save Theme To File” option is greyed out when the default theme is in use such that you cannot use that as a base for a custom theme. Would be nice to be able to generate themes off that since it has a lighter grey for the baked in UI elements than is found in the other packaged themes.