I have no idea. You can do about 30k for 401k with catch up contributions and another 8k in ira with catch up. Your employer can put in another 49k maximum. That’s not even 100k. Hsa is a backdoor Ira, so there’s 8.3k for a family. I guess it’s the rule that allows a 529 to become an ira now, depending on the state you can put 200-500k in one, but that’s a lifetime limit not annual.

I started looking into it, found cash balance plans that allow very high contributions to tax advantaged retirement accounts. However looks like something that is not available to the vast majority.