Why? Manifold doesn't know how correlated the markets are.

How would the math of this work for an AMM?

If you do a parlay at a bookmaker, you are gambling against the house. It's easy for them to offer such service and the house edge compounds for them with every bet. On prediction markets it's almost technically impossible imo to make parlays because it's different counterparties to bets. Unless if you actually make a new market where you resolve it based on the outcome of other markets. For example if these 3 markets resolve yes the bet wins, otherwise no. But then that's not really a feature.

Very hopeful to see this feature