Professor Joseph Patrich of Hebrew University Notes - No One Has Ever Attempted to Identify How Many Works Were Actually in the Library of Mar Saba at the Time of John of Damascus (Let Alone Those Which Are Now Lost)

Apparently, he has made a list of possible books that existed at the library in the sixth century, but no one has compiled a list of references for John. Patrich does have this interesting bit to say about the remains of the ancient library in modern times:

Many of the monastery's manuscripts were burned in a fire more than 250 years ago. Up to 1887 there were 706 codices in the possession of the monastery, when they were removed for their safety to the patriarchate in Jerusalem. Before 1887, fifty-five manuscripts had been taken from Mar Saba, finding their way to libraries and museums around the world. The extant Sabaite collection thus amounted to 761 codices, 129 of which were written in the laura by thirty-six calligraphers or scribes over a period of eleven centuries, from the ninth to the nineteenth. The major part of the collection thus consists of manuscripts that were written elsewhere. The earliest of the 129 written at Mar Saba are two manuscripts of the ninth century. The majority are from the sixteenth century (28), seventeenth century (22), eighteenth century (46), and nineteenth century (11). The most prolific scribe was Joannikios, who copied thirty-one codices in the eighteenth century. A possible connection of the Archimedes palimpsest with Mar Saba is discussed by Netz, adding a new dimension to the local library. [The Sabaite heritage in the Orthodox Church from the fifth century to the Present p. 10]