The question of concatenation

[Emma May Smith]

That's not exactly what I mean. I mean producing words by concatenation.

For the sake of example (Voynich sequences are arbitrary):

if ar maps to "ein" and d maps to "das", would dar map to "dasein"?

My apologies for misunderstanding you.

In answer to your question: I believe that changes can still happen.

• The a glyph [a] has a clear determining environment. It mostly precedes the glyphs [l, r, i, n, m]. It can and does appear otherwise, but much less commonly.
  
• I believe, and think there is evidence to support, that the glyph [a] is a variant (or somehow related to) [y]. In my hypothesis, when [y] is followed by [l, r, i, n m]  it becomes [a].
  
• So the word [dy], when a final [r] is added, becomes [dar].
  
• Whether or not that indicates an actual change in the plaintext, or is simply how the script works, I don't know.
  

As with my first answer, these are my opinions. They constitute my best guess as to how to the Voynich text works. Nothing is definite.