Member Junction
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    WhiteboardToolRoster: readonly WhiteboardTool[] | null

    A host-supplied subset of the board's tools. null means "all of them" (today's behaviour).

    The roster is ONE fact read in three places, so a tool a host hides is hidden everywhere a user could reach it: the floating toolbar, the single-letter keyboard shortcuts, and the right-click "add … here" actions. Hiding only the toolbar button (CSS) leaves the other two doors open, which is how a consumer ended up with learners able to press w and place an HTML widget on a board whose toolbar showed no such tool.