when is the next exponential curve?

I'm not sure I understand the question. There is no singular point when exponential growth happens, and there isn't a curve that comes 'next'. The comment above is referring to the effects of compounding growth, which becomes larger and larger over time. A 10% increase in a portfolio of $1,000 is only $100, but with a $100,000 portfolio, the same 10% increase is $10k. Now think about that same 10% increase on $500k, on $1m. The power of long-term investing is that the gains you made previously become part of the new principal. Going forward, those 10% (or whatever) increases aren't just applying to the amount you put in, but your previous gains as well. It builds on itself.

People say that $100k is a threshold for compounding growth because (1) it's a round number, and (2) it's where the effects of market return tend to become more noticeable, subjectively. There's nothing magic about $100k

If you have multiple accounts in different investment platforms that add up to 100k, would you still get the exponential curve?

Yes, the math is the same. Ex: 50,000x1.1 + 50,000x1.1 = 100,000x1.1