I'm mostly talking about people that, for one reason or another, appear to wander around with no clear career progression or direction, so it looks like they are "junior" in experience despite being "senior" in total years worked.

And I think that re-doing careers by switching professions (as you say, chemist -> QA) is different than re-doing career in the same profession. Something like the former is different because it's easier for companies to treat you as a clean slate if you switch to something that has little overlap with your former profession. But I want that clean slate treatement just re-attempting my profession.

For instance, maybe I want to re-do my entry level years because I never got into Computer Science, and would like to get an internship at a leading tech company, because that is a better start than my reality, which was just graduate with no internships, no support group of professionals, nor recommendations for good companies. It was just me going solo and blindly applying to local jobs at Craiglist for low-budget clients.

So yeah, I'm not talking about career switching into another profession, but more like hitting the reset button on one, to do it better the second time around.

Okay that is helpful. In my experience, this situation -> people that, for one reason or another, appear to wander around with no clear career progression or direction, so it looks like they are "junior" in experience despite being "senior" in total years worked. has always been that the person wandering didn't know what they wanted, and if it had been years, didn't have tools to figure out what they wanted.

I am reasonably certain there are other explanations/causes but the three cases I can recall easily were all that the person got into a career in computer programming because someone one else told them they should. And they stayed employed but they didn't have any idea about what they wanted to do so they changed jobs for all sorts of reasons, a girlfriend, a pay raise, a manager that kept bugging them at the old job. All of the change reasons were external to their career path.

One really wanted to be a musician. They could talk on and on about different styles and influences. They lit up and were on fire. One was lost, they had always had their life planned out for them by others and they followed that plan until it ran out (just after graduate college and get a job). And they never previously had been required to create their own plan. I didn't get to talk with the third person I can remember because they moved on to a new position before I had that chance.

If that resonates with you then my advice is to work on figuring out what you really care about. And I recognize that isn't an easy task, it was simple for me I was fascinated by computers and the systems you could build with them, so much so I build stuff just for fun. But a good way to search for the things that you care about are to explore different things (very hard to do as a single breadwinner in a family). As I told my musician friend, even if you're not an artist with a signed label contract, you have a understanding of what they are going through and you can write code. Can you find ways to help other musicians that way? Or music lovers? Or screenwriters trying to match music to scenes? or hospitality businesses wanting to influence the mood with music? You can get quite meta and still exploit the experience you've developed in an area you care about.

Without an amnesia treatment there is only so much you can reset :-) Mostly folks learn basics about work (its not always fun, how you work can be as important as what you get done, your boss may be an idiot but it doesn't change the fact that they are your boss, etc). So instead of 'resetting' it's more like vectoring. Now that you've been in the career for a while, if you know what you'd like to be then imagine you have reached that point and and then try to imagine plausible steps that you would have had to take to get there.

I don't take it as necessarily an implication of accumulated failure.

Career paths just tend to end, somewhere somehow. Might flame out. Might get a bad rep. Might be doing just fine but that tech & corp might just be leading to "going nowhere", coasting or the path vanishing. Be on a road long enough, you eventually discover it ends, be it accumulated choices or "just does".

At some point you need a change of direction. Might even be the same direction, you just have to get on a different road that actually continues that way. I'm still doing what I always liked doing, I just swapped out the technology & clients for something more modern.