It may be helpful to provide the incident number in an Assignment for easy reference by the user with responsibility on the assignment.
This article describes how this can be accomplished.
1. Open Service Management Administrator
2. Open a New Definition Set
3. Open the Task.Assignment Object
4. Add a new field:
name - ParentID
type - Number 10 digits
Show as desired on the Task.Assignment Form and grids as needed
5. Commit the Definition Set
6. Open the Incident Object
7. Edit the relationship "IncidentContainsTask"
Push Data - Left Side = Task.Assignment.ParentID, Right Side = Incident.IncidentID
8. Commit the Definition Set.
9. Perfrorm an IISreset
Now that you have the field available in the child Task.Assignment object you can use it on grids or panels as you wish.
The example above is for Incident.
You may wish to push the data for Change or Problem as well.