No scroll capability in Deneb Gantt visualztion

Greetings.  Have a use case for a Gantt like visualization. Landed on the Gantt rendering in the Deneb visual provided by David on his Github repoistory for Showcase Samples. Great documentation, easy to configure and get something stood up.  I'm being stumped though on how to get the scroll bars to display on the visual.  I've gone into the Format editor and enabled the scroll bars to be visible when editing.  I can see them inside the editor.  However, when I render the visual there's nothing there.  Below is a screenshot of the settings.  I went throgh the Vega documentation searching on the keywork "Scroll" without any luck.  Any ideas on what is probably a simple thing I am missing? TIA. dm-p