Containers and agents have adjustable height title bars.
The height of the title bar may be changed by dragging the bottom of the (selected) container's title bar, or the top of the agent's title bar, to make the title area taller or shorter. Within the exposed 'title' area, subtitles, body text or table data is also drawn if there is room, as on a normal note icon.
The height of the title bar may also be changed by setting the $TitleHeight attribute. The attribute uses Tinderbox map units for its value.
To 'hide' the viewport area of a container, set the $TitleHeight to equal $Height (or for agents, $Height - 0.1). This makes the map icon look like a normal not except the 2 bottom (note) or top (agent) corners are rounded. While the viewport hidden, it is not possible to double-click drill down but its shortcut (Cmd+Opt+Return) will work.