Thank you for chiming in. I was using the Default style. From that I created a New style, and called it Nick. I inserted your line at the place that seemed right to me, and bingo! The nickname, if entered for an individual, appears in brackets right after the given names. Exactly how I want it.
However, all the boxes for individuals in the Dynamic tree have less height now, and hence they display fewer lines - which, to be clear, is not what I want. I wouldn't know how that changed behaviour is possible, because I didn't change anything other than inserting "your" line and it contains nothing about dimensions. In fact, I don't see anything about height in the code of Nick, only about width.