Thank you for this comment, I understand:-
Comment by Marc Sabatella:
You shouldn't need to be using the Mixer to change volume mid-score - that's what dynamic markings are for (see Dynamics palette). Similarly, to change from arco to pizz, simply add the appropriate marking (see Text palette).
But, what is the purpose of this list, in The Mixer, (see file below).
That is meant as a way of changing the sound for the entire score, not for mid-score changes. And really. even if you want the strings to play pizz the whole way through, you wouldn't normally use the mixer for that, you'd simply add the "pizza" marking to the beginning of your score. After all, the musicians reading your score can't see any fancy mixer magic you do. They only see what's printed on the score. So in general, if there is something you'd want to hear in real life, it should be marked directly on the score. And then, in most cases, it will also play back correctly.
The main intended use for the mixer isn't changing things like arco and pizz - it's for selecting which of the various guitar sounds you want to hear for your guitar part, or which of the various electric keyboards you want to hear, etc.