It is possible to create arbitrary user data that can be attached to any object. This user data can then later be used at shading time by specific nodes with a user prefix.

Information about User Data shaders can be found here.

 

The convention used to store the user data can be found in different data types such as color, float, etc. For example:

 

If display color of an object is enabled we will export the 'display_color' RGB as a user data.

A video tutorial that demonstrates the use of the User Data String shader can be found here.

A tutorial on how to use the User Data RGB shader can be found here.