a) an easter egg that has no effect on LV programming, such as changing the color of the splash screen in LV6.0 or b) a feature of LV that we hope to release to customers someday but which is currently so bug ridden and/or hard to use that we can't afford to officially support it.

99% of undocumented features are in category B. Generally we password protect the block diagrams of VIs that use these features. But LV is a huge program and we ship hundreds of VIs with LV and sometimes we forget to put a password on a particular diagram and someone discovers a feature that they can copy off of those unlocked diagrams onto their own VIs. Such features are "use at your own risk." If they worked the majority of the time in a reasonably expected manner, we'd probably have released it to customers... after all, if we kept new features secret, no one would pay money to upgrade, so it is to our advantage to tell customers about new things.

Some of these are really cool. Some of these are kinda dumb (really awful user interface is a legitimate reason for us to hold off releasing a feature). If you discover one of these undocumented features, you probably shouldn't use it in any production code. We might not support that feature in a future LV version or might have changed it so much as to break your existing VIs. Don't call our Application Engineers about such features -- they won't be able to help you. Enjoy these as bits of candy and glimpses into the future of LV, but don't think of them as part of your daily lunch.