I'm a mod at Writers.SE.
Requests for words and phrases used to be on topic here on EL&U; I'm not certain what the precise current status is on these, but Against single word requests and Single word requests, crosswords, and the fight against mediocrity express the problematic nature of these questions, and (this is my impression on skimming these topics...) at very least, they demand a high level of research and detail of such questions on EL&U.
Writers.SE doesn't accept such questions and never has. (We have, in the past, accepted "please critique this piece of writing" questions, which is not entirely dissimilar; however, these have been taken pretty much off-topic, for much the same reason as phrase requests on EL&U.)
If rephrased as a typographical question, e.g. My table of contents looks awkward due to long, repeated phrase in many headers, I think Writers could take this. This isn't "what's a shorter phrase for ," it's "I'm having a problem with my table of contents" — which is (A) a solvable, answerable problem, and (B) a problem other people probably also encounter. That'd take a fair bit of work, though, and it would invalidate a whole bunch of the existing answers. If you'd like more input, you might open a new question at Writers.SE instead of trying to migrate this one.
Minor point — As for the flag, a flag can be helpful without necessarily dictating action. Your flag raised a valid concern; it wasn't unhelpful; it didn't need to be rejected. It just also wasn't persuasive enough to spur anybody to action — or maybe their response was to check with us at Writers, and we turned the question down.