A good match, perhaps from the Zürich area...

[Bernd]

There's what we see, but also what we can derive. Someone starting a word with "k" is unlikely to be writing in Latin.
What we see is k, u, and a ligature of c+3 with a macron. (I just use 3 as shorthand for the symbol).
If this were Latin, the way to read it would be kucent, which doesn't exist. Cucent doesn't either, by the way.
In German, the 3-symbol and the macron might function differently, so we need to go beyond what we can see to figure out if the word makes sense.

I know I like to play Devil's Advocate, but I still think the a priori assumption that the marginalia consist of valid words or phrases has little ground. This does not mean we should not try to make sense of them, maybe they consist of exotic spelling and abbreviations, but we must not fall into the trap of the countless Voynich 'Theorists' who perform mental gymnastics to make 'sense' of a vord or line of VM text. The main issue with marginalia is the small sample size.

The second issue here is that we are not dealing with one or two unreadable words in an otherwise readable text but a completely unreadable corpus. Even if it looks familiar. That is the main theme throughout the VM. Imagery, Voynichese, Marginalia.

I find the matches in this thread extremely convincing. Supposing the authors of the marginalia and the authors of the manuscript shared the same time and geographical location, how does this affect the list of possible plaintext languages for the manuscript itself?

I think there is some evidence that the person who wrote the marginalia and made the drawings associated with them might be the same person who made all drawings in the VM. I will make a thread about what I found.

I would be extremely surprised if it turned out that this marginalia (and hence the rest of the VM) wasn't a product of someone who lived in or around Zurich/Northern Switzerland/Southern Germany between 1410 and 1450.

Yes, I do agree with this. Early 15th century Switzerland is by far the most likely place and time for the creation of VM imagery and marginalia. Whether the month names and quire numbers really require a travel to France, or whether they could also have originated in Switzerland is another matter. Given that Switzerland borders South Germany, France and Italy, I do not think it is entirely unreasonable to assume that the entire VM was created in Switzerland. But honestly I would not rule out anything at this moment.