While building some item prototypes, there is no way to map the prototype to an interface.

This is because zabbix doesn’t “know” the interface prior to being added to a host. However, some details could be passed to the discovery rule as additional macro {#INTERFACE} (or something similar) via custom discovery script. Then macro's value could be used as mapping to one of existing interfaces.

This would be very useful for situations where the host is running multiple applications on multiple interfaces, and we need to report-back the appropriate interface/application in the trigger.