OptionalheaderActions?: CubeHeaderActionsThe host's own buttons, at the end of the header, e.g. Studio's Add MatView
OptionalinitialDocument?: CubeDocumentThe cube to open; an empty one by default
OptionalinitialLambda?: CubeInitialLambdaA lambda the host opens the page on, read into the cube (Import Pure, PLAN §11.18), e.g. Studio's materialized view to edit
OptionalinitialSource?: CubeEntrySourceA source a link asks the page to start with, on an empty cube (spec §17.15)
The Legend Cube page: the query above, its results below, both always shown (PLAN §7.1); hiding the graph leaves its header. A node's editor floats below the node (PLAN §11.8). The host gives it the engine, the models and the application store; the page's state lives as long as the page.