The best tech writing managers will have deep knowledge of the discipline, but it's not necessarily a prerequisite.

You've described the predicament I'm in right now—I want to be a great manager, but I don't have experience in the industry that I'm interested in. I have many years of technical writing management and technical writing experience, so I guess I do have "deep knowledge of the discipline", but the discipline for my target industry, software, operates differently. For example, my company doesn't use docs-as-code or Markdown, we just use Word files.

Right now I'm at a crossroads. I would like to break into software, but I'm not confident I'll be able to do a good job without knowing the industry. I've been thinking about finding a job as a technical writer in software, learning that industry, and then hopefully getting promoted back into management or hired as a manager (I'm very underpaid so I could make more money doing this). Or I could try to get a job as a manager in the industry now, make way more money, but risk being a not-so-great manager, which may hobble my career in the long term.