An INTEGER enumeration (preTrigger, postTrigger), read-create, choosing whether the timeline keeps the data collected mostly before or mostly after the trigger fires. This determines whether the captured window shows the buildup to a triggering event or its aftermath, changing what an engineer can diagnose from it. For example, choosing preTrigger for a sync-loss-triggered timeline preserves the signal behavior leading up to the loss, while postTrigger would instead show how the link recovered afterward.