Jira Workflow Toolbox uses field codes in many conditions, validators, post functions and calculated custom fields.

Field codes are used to access and manipulate data from:

• normal custom fields
• system fields
• virtual fields
• internal fields
• parent fields  

Writable virtual fields

When a value is written into these fields, a feature or system field of the issue the field belongs to will be modified. These fields are also readable.

Values returned when reading virtual fields

For every virtual and custom field in a subtask, there is also another virtual field representing the same field in its parent issue, making it very easy to read and write parent's issue fields.