Function sheet_ordinate_schema 

pub fn sheet_ordinate_schema() -> Value

The Ordinate set dialog’s schema, in the inputParamsSchema vocabulary the shared form engine renders.

TWO reference fields rather than one list with a magic first row: the datum and the members answer different questions, and datum’s ✕ has to mean “this set has no origin any more” while a member’s ✕ means “drop that one value”. A single list could not tell those apart without counting rows.