To find out which holidays refer to a specific recurring holiday via a conflict rule, select that recurring holiday and then use the References to this Holiday Rule menu item from the recurring holiday popup menu.
The search lasts a few seconds and, if any holidays refer to the selected holiday, a dialog appears that displays these holidays. These references come from holidays that refer to the displayed holidays through conflict rules.
The recurrence rules for the holidays displayed as a result of that search will be broken if the recurring holiday on which this search was based is deleted.
See also: finding referrers to a holidays set.