Zoltor, the only reason it would ever be a "bad idea" to change the note tag contents of an Actor is because most script authors don't actually bother checking what the value of the note tag is -- instead, they assume that the value won't change and cache the information. For some reason, they assume that this will bring some "performance benefit" over making a call to the note method which -- at its absolute worst -- generates a single string which will most likely either be used or garbage collected.
Compared to the egregious abuse of iterations, for loops, poor Bitmap management and overall slipshod programming I've seen from the majority of the scripting community, generating a single string every once in a while hardly seems like a problem.
By the way, Killock, the answer is a very simple script call.
$game_actors[0].note = "asd#{$game_variables[1]}Z"This doesn't mean that scripts will automatically be aware of the change and use it, though -- in fact, it's extremely likely that they won't simply due to the way most script authors write their scripts, as I explained above. Try it, but I can almost guarantee you that it will not work without modifying whichever script is loading the note tag information for use.
Also, Shaz, the changed note tag contents will be stored in the save file -- after all, the note tag is simply an instance variable.
Edit: I also don't have Ace open, so I could be completely wrong about the details of how to set the note (I can't recall how Ace stores the information from the database in an instance of Game_Actor). If anyone else sees this and notices that it's incorrect, please provide the correct script call.