Context Data in Nintex Workflow represent values specific to the workflow, the context of the item and the current task within the workflow. As an example below are some of them

Initiator: The username (domain\username) who caused the item to be entered into the workflow

Item URL: The URL of the item in workflow

The complete list of Contex Data items and how to manage it is described  in Nintex Workflow User Manual.

Designing custom Context Data usually include the implementation of specific handler(class). In Nintex Workflow API  for this purposes exist class ContextDataItemBase, from which all Context Data items usually inherits.

The implementation of Context Data for returning approvers comments in XML format is presented below

Below is shown page for managing Context Data with custom Context Data added  and Insert Reference dialog that demonstrates the usage of custom Context Data when designing workflow   

Now our goal to automate the deployment of Context Data. For example, it is possible to create Data Context item during feature activation. For this task we’ll use method of class CustomCommonDataCollection (in namespace:Nintex.Workflow) from Nintex Workflow API:

Adding Context Data item  in Nintex Workflow Management (shown below)

is equivalent to calling

You could grab the source code for the project that demonstrates how to provision Context Data here.