How would you parse or diagram "This is beyond sad"? My best guess is that the prepositional phrase is elliptical, omitting the true object (necessarily a noun), such as "something," as in "This is beyond (something) sad." I think this analysis preserves the meaning of the sentence and accounts for the accepted functions of nouns to serve as objects and of adjectives to modify nouns. Thanks for your insights.
This use of "beyond" is metaphorical. It suggests that there is a range of possible emotions about the situation, "sad" is the most extreme one that has a name, but the actual emotion is even further in that direction. Another way to say it is "This is more than sad".
The death of a single person is sad. The death of an entire family is beyond sad.