I can’t speak for the person you replied to, but I work for a software company that is always on the lookout for mechanical engineers who can write code. It’s a pretty rare combination.
Any suggestions for a mechanical engineer who has some coding aptitude and wants to switch careers? I'm self taught and have mostly worked on hobby projects. I have some professional controls experience programming automated machinery (PLC). My lack of formal CS training seems like a real barrier to jumping into a full-time software role.
It's true, you might be able to find a slow career move where your roles take on more and more code until eventually pure programming rolls trust your experience. However if you're looking for a faster move look into night classes, if possible. You can get a computer science degree for much cheaper in a couple years of just doing night classes along with your work. It can be hard to balance all that but career changes are usually difficult to navigate. I wish you luck!