[Question] Who is working on finding “Cause X”?

As a community, EA sometimes talks about finding “Cause X” (example 1, example 2).

The search for “Cause X” featured prominently in the billing for last year’s EA Global (a).

I understand “Cause X” to mean “new cause area that is competitive with the existing EA cause areas in terms of impact-per-dollar.”

This afternoon, I realized I don’t really know how many people in EA are actively pursuing the “search for cause X.” (I thought of a couple people, who I’ll note in comments to this thread. But my map feels very incomplete.)