If you want to call max with two output arguments you need to combine lines 12 and 13 together and add square brackets. Use this:
[valueMax, iMax] = max(heuristicValues);
Alternately add the square brackets and then use the same approach with the ellipsis that you did to break the assignment statement on lines 8 and 9 across two lines. So this would also work:
My personal preference would be the first approach, the whole statement on one line, unless that results in a really long line that would require my Editor window to be very wide to see the whole line. In that case I'd probably leave the equals sign on the line with the output arguments and put the max call on its own on a second line.