Make a new Incident relationship
Select Incident as the Other object
Set a display name and internal reference - i.e. IncidentAssocIncidentForCallHistory
Set the Cardinality: Zero to One on the left and Zero to Many on the right
Set the Fields to Profile link on the left, RecID (Primary Key) on the right
Leave all other settings at default and save the new relationship.
Create a new child panel on the layout/formView in use.
Name the Child panel (tab) - i.e. Call history
Click to select the Object
Use the 2nd option: "Use only rollup relationship(s) to grandchild objects"
Select the Business Object Incident
Add 2 rollup chains
Name Each appropriately - i.e. CallHistoryAsCustomer and CallHistoryAsReportedBy
Check the box for "Show rollup records by default"
The first chain should have these relationships defined (for Call History as customer):
The Second chain should have these relationships defined (for Call History as Reported By):
Save the Settings and populate the remaining child panel settings for layout, form etc as normal.
Now we can see all records in a single tab where the Customer on the current record is populated either in the Customer field or in the Reported By Field.