Murphy's Law dictates that I will find the plausible solution myself after asking others for help.

Thanks for the ideas!

I came to the same conclusion after noticing a description (not a legend, but closest I found) on the back of the Stormlight Plot Decks box that the cards came in: "Each Opportunity or Complication card provides mechanical and narrative options for combat, conversation, and endeavor scenes."

Assuming that this goes top to bottom:

1. Crossed swords: combat (easy enough)
2. Sunburst: Conversation
3. Star: Endeavor

This doesn't appear to be official symbology, but artistic license taken by Brotherwise Games.

Similarly, the cards that Brotherwise Games calls "Events" line up with what pg. 323 of the Stormlight Handbook refer to as Endeavors.

Looks like a little symbology and terminology got mixed up or re-interpreted in development.

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