“I’d be interested to know where and when the system is first attested, and for how long it was used, the range over which it is known to have been used, and whether it was first devised for secular, or for religious libraries, or appears in both from about the same time – whatever that might be.”

I don’t know where this indexing system was first attested (it may go back to ancient times) and whether it was originally devised for secular or religious libraries (it’s possible that no one knows the answer to this). If you have an interest in ancient and medieval indexing systems for large datasets, I’m sure you can find research sources to follow up your questions.

“He [Brunn] also concluded that the Voynich ‘vords’ weren’t words at all.”

I have not concluded that the Voynich tokens are not words. I stated in this blog that I don’t think most of the labels are words, at least not if the spaces are taken literally, but I think it’s too soon to generalize this impression to all the text.

“Another interesting decision was made in the catalog of the library of the Augustinian
Friars at York, compiled around 1372. Here, the cataloger assigned letters of the alphabet to
each book in each subject class. Letters were repeated or combined with symbols when necessary. In this way, a book listed by its letter then its content clearly shows which titles are
contained therein, avoiding the problem of titles running together.[44] While these organizational
schemes may seem to modern librarians as “stopgap” measures which do not fully compensate
for lack of access to each title and subject, they obviously served their purpose in the libraries
they described.”

I have that information from
Beth M. Russell, ;Hidden Wisdom and Unseen Treasure: Revisiting Cataloging in Medieval Libraries,
[in journal..] Libraries and Classification Quarterly, 1998, vol. 26, no. 3, p.21-30.

The source which Russell cites in her footnote [44] is
Dorothy May Norris, A History of Cataloguing Methods 1100-1850: With an Introductory Survey of Ancient Times, (London: Grafton & Co., 1939) p.51

The part which intrigues me most is where you say, “I learned that this is a medieval indexing system, one that was designed for large datasets.”

I’d be interested to know where and when the system is first attested, and for how long it was used, the range over which it is known to have been used, and whether it was first devised for secular, or for religious libraries, or appears in both from about the same time – whatever that might be.
DId your source cite many non-German examples, and especially from fourteenth century?

With regard to the Voynich glyphs, it occurs to me that if you can correlate the ‘mi mo mu’ with specific glyphs, Julian Bunn’s colour-coded pixel-grids may be of value to you. He also concluded that the Voynich ‘vords’ weren’t words at all.

Thanks.