This placement does well wherever the word becomes the main tool of the job. Law, especially the kind decided by the wording of an agreement rather than a brawl in court. Diplomacy and international communication. Editing, translation, literary consulting, the interview side of journalism. Any board-level work where shareholders' interests have to be reconciled through a document. The common thread is that the result lives or dies on a sentence, and a sentence is exactly what this mind is built to weigh.
Mediation and negotiation fit almost perfectly. So does HR in a large company, particularly the internal-communications and conflict-handling end of it. Mercury in Libra reads the positions of the different sides quickly, can re-frame a complaint so that it can be heard without offence, and often lifts a stuck situation out of deadlock with a single precise line. In my experience the strongest careers here are built on this re-framing skill rather than on raw decisiveness.
The creative industries suit it too, especially anywhere the work turns on text and form: advertising, copywriting, brand strategy, scriptwriting. Here Mercury in Libra runs at full stretch — a feel for the rhythm of a phrase paired with the knack of holding the client's interests, the audience's and the aesthetics in mind all at once. It's less a matter of one big idea than of finding the version of the idea that everyone in the chain can live with.
Where it tends to struggle is anywhere that calls for fast, hard, one-sided decisions made in public and owned alone — the front-line crisis manager, the prosecutor in a case for the prosecution, the field commander. Not because the job can't be done, but because the toll on the nervous system runs high. The most settled careers for this configuration, in my experience, tend to be built in a pair: someone alongside makes the blunt, unpopular calls, and the person with this placement gives them a clean, precise form in which the decision can be shown to the world. Treat all of this as a lens for self-reflection and a bit of fun, not a prescription for what you must do.