This question is motivated by this question and its answers.
Firstly, I wish to display "O(x)" instead of "x" as the callout labels. When I do this
lbls = Map[HoldForm["O(" #1 ")"] &, funcs];
I get double parenthesis for the fourth element. How can I avoid this extra parenthesis without altering the formatting style?
Secondly, How can I display only the callout labels without the callout lines?