There's also a question of making the market. I've got these really weirdly-broad skills. LinkedIn is not great for finding the niches I want to fit. I suppose there's HN's "Who Wants to be Hired" threads, but that's risky if you're already employed. I'm obviously networking already, but what else is there?

Add it to the cover letter

Unfortunately that is one of those things, everyone has to write, and almost no one reads.