As of the beta 3 release, the Analog Buffer has been deprecated. It has been replaced with the OpAmp, which is consistent with the name used in the device documentation. The OpAmp provides all the functionality of the Analog Buffer. Designs using buffers will still build and work. The component itself is still available (in the Deprecated folder of the catalog) if you set the "Show Hidden Components" option in the Tools->Options dialog for Design Entry.