Usually what you want to do is get in to one of the pre-sales teams so you are part of the sales process but can still stay technical. This will let you see the sales process and start developing new skills. This is usually focused on the enterprise market where the pricing justifies a more expensive sales process.
You can also do this at a startup but it won't teach you sales typically. Startups are learning how to sell themselves usually, so they don't have a mature sales process or people so if you are wanting to develop those skills go to one of the big consulting firms, or CRM companies etc.
I always envied them for not having to spend the time to "productionize" their work.
I am curious why you feel it is a demotion? Money, title, prestige or ? Not judging, honestly curious.
It's because the skillset is rare; hospitals aren't going to buy some medical equipment from some sweet talker in a suit. They prefer a nerd who understands exactly what they're selling and what the advantages and disadvantages are, maybe even explain training needed. I had one oscilloscope sales job offer, where the boss insists that the hardest part is understanding the tech, and the sales part is easy to train.
Many sales roles give commissions, which can come up to a hell lot.
Software probably doesn't involve the dirty details anymore, but I imagine things like selling a database, AWS-type service, military technology, machine learning, and so on.
As far as I can tell, many things are limited only by the amount of complexity people are willing to handle and the workload they can support. If you're okay pulling a work-day with co-workers and then another one when they leave, then we understand each other. Some people can pull off 16 hour work days or more, even during the week-ends, even during holidays and think about the product all the time. Some are great and can do that in 4 hours, I personally can't.
Find things that suck, fix them, institutionalize that knowledge, document everything, prepare for the eventuality of your disappearing, build an organization, train people to think like that, read a whole lot, become good a things, add a lot of value, become someone you would fear if they were a competitor, have very high expectations of yourself and be afraid to disappoint yourself tomorrow, experiment, demonstrate by building things and implementing things, not just as "ideas" but actual outputs, either codes/graphics/copy/documentation/training manuals/videos. Go for it.
*Yes, I looked you up. I'm that good.
Promise not a stalker!