You can delete line/assembly associations that have not been used to define a repetitive schedule.
Navigate to the Repetitive Line/Assembly Associations Summary window.
Choose Find from the Query Menu.
In the Find Repetitive Line/Assembly Associations window, enter your search criteria. The results display in the Repetitive Line/Assembly Associations Summary window.
Note: You can delete line/assembly associations in either the Repetitive Line/Assembly Associations window or Repetitive Line/Assembly Associations Summary windows.
Select the Line/Assembly association.
Choose Delete from the Edit Menu.