[MarketPress eCommerce] PayPal Chained Payments

How do I enable PayPal Chained Payments? I've enabled the global cart, but only see PayPal Express Checkout as a possible global gateway.

According to the documentation, When the global cart is active, only the PayPal Express Checkout gateway is available for use on the network.

But to do chained payments, the documents say In the case of MarketPress, we provide this via the PayPal Chained Payments gateway.

Where do I find the Chained Payments Gateway?