Deleting drivers is only possible of you are using a detached scenario. See working with a synced scenario for more information about the differences between synced and detached scenarios.
To delete one or more drivers from your scenario:
Open the list menu in the upper left corner of the List panel and select the Drivers option. The Drivers list opens.
Select the check box beside each driver you want to remove in the grid, and then click the Delete button on the List panel tool bar. Alternatively, click the More button in the upper right corner of the List panel and select the Delete Drivers option. The drivers are deleted immediately (no confirmation required).