BFEVFL is a binary file format for event flows.

Read BFEVFL article on BotW wiki

Usage in Link's Awakening

BFEVFL is used as the underlying format for event flows in the release versions. Both flowcharts and timelines have .bfevfl as their file extension. Flowcharts are stored directly in rom:/region_common/event, and timelines in rom:/region_common/event/tl.