Even though a Vivado project has not been created on disk, the in memory design is available in the tool, so from the Tcl shell you can open the Vivado IDE to view the design.
Non-Project mode enables the use of the Vivado IDE at various stages of the design process. The current netlist and constraints are loaded into memory in the IDE, enabling analysis and modification. Any changes to the logic or the constraints are live in memory and are passed to the downstream tools. This is quite a different concept than with the ISE tools that require saving and reloading files.
Open the IDE using the start_gui command.
Vivado% start_guiThe Vivado IDE provides design visualization and exploration capabilities for your use. From the Vivado IDE, you can perform further analysis and constraint manipulation on the design.