OptionalclassOptionalcontextThe catalog — page 1's search/browse.
OptionalhomeThe cell the call is being inserted into — page 2's anchor for bare references.
Optionalon"That one" — a double-click in the list. The host takes its own default action.
OptionalonThe assembled call from page 2, on every change — =SUM(A1:A5,B1).
The selection changed (a click, an arrow key, or a new query landing on its own top row).
Which page is showing. CONTROLLED: the host owns it, because its action row depends on it.
The chosen function, and the second page's subject.
OptionalworkbookEvaluation/resolution context for page 2. Defaults to the enclosing WorkbookContext.
Class(es) for the showing page's root.