From Xojo Documentation
Controls whether scrollbars are shown when scrolling is not necessary to bring additional text into view. The default is True.
The vertical scroll does not appear until there are more items in the ListBox than can be viewed at once. If AllowAutoHideScrollbars is False, then inactive scrollbars are shown until they are needed to bring additional text into view. AllowAutoHideScrollbars can be set at design time or runtime.
This example turns off AllowAutoHideScrollbars.