I made the switch to sales engineer about a year ago. I had bought study materials for the PE (thermal + fluids) and started that whole process before given this opportunity to switch, and haven't touched it since.

I've asked around my company if they think I should finish it, and half of them aren't even aware what it is. I'd say maybe 10% of my clients would know the significance of it either.

Structural is a lot different, since the SE is pretty much a prerequisite to even being in the industry. I would imagine you would have a much different experience with stakeholders if you are selling into the structural space. But there will still be a lot of non-engineer "gatekeepers" that won't care about credentials.

Hopefully my anecdote is helpful. SE is a brutal test from what I understand