Is it possible to change annotation next to the boxes from score to symbols?
I'd like to change it to
Blank if correct, "O" if skipped, and "X" if incorrect.
From revision r1271, try something like that for Edit/Preferences/Project/Questions annotation text:
("%W" eq "V" ? "O" : %M==%S ? "" : "X")
%W will be substituted with a code that explains the way the score has been calculated ("V" means that no box has been ticked),
%M with the maximum score (score for a perfect answer), and
%S with the score for the student.
%W has been introduced in revision r1271, but the others can be used in older versions of AMC.
Brilliant. Worked right away. Thank you very much.