From an event that shows up on an active channel's grid, you can select the option to add the event to an existing list or remove it, if that event is already an entry on an active list.
The default procedure is:
Open an active channel of events.
Right-click a specific event on the channel grid, and choose Active List > Add To > Other.
The Add to Active List dialog appears.
Note: The options Untrusted List and Trusted List apply to event fields that are address related.
Browse the Active Lists resource selector to locate your active list and select it.
The selected active list's entries are displayed .
Click OK.
Tip: If adding events from the active channel to existing lists is a frequent task for you, you can add your collection of frequently-used lists directly to the Active List option. That way, the lists are displayed instead of the active list resource tree.
Follow the instructions in Customizing the Default Selections for Active Lists