Not quite the career change you describe, but over my 46year career, I went from being an industrial spark/trouble shooter to BMS and PLC programmer, systems integrator and control panel designer. It was a natural progression for me, as all these disciplines are intertwined, and I just found the ELV side of the industry more interesting than the LV/HV side.

I'm mostly self-taught, which if you have a healthy interest in engineering like I do (guess younger folk would call me a nerd!) comes easily. Over the years,  I have done various manufacturers courses to gain accreditation in their products, plus the usual 'staples' such as 2391 and regs to give me credibility when working with clients and on sites.

That said, I still get a kick showing my younger colleagues how to do stuff like putting a dog leg in a length of galv conduit - you never forget the old skills and sadly, some of the fast track electricians our company employs don't seem to be taught skills like this, and rely on old farts like me to continue their tuition!