The Draco Trunk is a component in the Nooleus First Stage rocket. It is a medium-sized premium part module that attaches to either the Draco Crew Capsule or the Draco Cargo Capsule.
It holds 6 Cargo items and, like the Orion Service Module, has integrated solar panels, which continually keeps the spacecraft batteries fully charged.
When a capsule is attached on the Trunk, it seems to be only possible to access the Trunk's items. But you can access the capsule's items by going to the pressure view and clicking the pressurized interior of the capsule. The pressure bar should show the pressure of the capsule. Now the capsule is selected and you can access it's items. To switch back to the Trunk, unselect the craft completely and reselect it again.