PS8740B is Host side Mux, used near the display source / USB host.
PS8742B is Sink side Mux, used near display sink / USB device.
Hence in a notebook design, we use PS8740B, since notebook is the Host and Display source.
In a dock design, the dock is receiving USB / display data (and providing it on downstream USB / DP / HDMI connectors) and hence uses the sink mux, PS8742B.
Lastly, source code and PSoC Creator projects are made available for CCG4 Dock Reference Design. Please go here and download the reference design package provided under 'related files'.