The Dragon trunk is mostly a simple structure used to provide an interface between the second stage and the Dragon. It carries the solar panels, and allows for carrying bulky unpressurized cargo. It has no orbital maneuvering system, docking module, or anything else of use.
On the other hand the Chinese Shenzou design is heavily influenced by the Soviet/Russian design of the Soyuz. In that model, the spacecraft has three modules, a propulsion module that is unpressurized at its base. The middle module is the reentry module, and the top module is the orbital module.
A pedestrian benefit of this design is that there are two rooms, while in orbit, with the washroom in one for some modicum of privacy.
When a Soyuz or Shenzou is done with its mission it discards both the Orbital and Propulsion modules and only the re-entry module returns. The Chinese advancement over Soyuz was to leave that Orbital module behind for science missions. A clever use.
It seems unlikely that they could 'stack' them up, since the interface between the modules does not seem to be the kind that would allow reconnecting modules in orbit after use.