You can now start a Demand Gen campaign from an existing PMax campaign.

The new "Prefill campaign" option is in beta. When you create a Demand Gen campaign, Google can use a PMax campaign as the starting point and import:
audience settings and targeting signals
existing image and video assets
core campaign configurations

Google AI also suggests a bidding strategy and target CPA, a daily budget, and Demand Gen best practices.

Spotted by Thomas Eccel.