I'm currently SE2 in my company, which is the earlier side of mid-level and am trying to make progress to SE3 and then senior engineer. Knowing that, how can I start making headway towards that SE3 promo? Do I need to be able to draw the line between my work and business impact?
Some fundamentals I believe apply to any promo:
At your stage in career, I wouldn't expect the ability to draw large, clear lines between your work and business impact: That's more of an expectation at senior from my experience. I think in your situation, at a high level, focus on knocking it out of the park with the projects you are given and don't worry too much about the business impact of each project.
In terms of what an engineer on the earlier side of mid-level can do: