From Xojo Documentation

Property (As Boolean )
aListBox.HasHorizontalScrollbar = newBooleanValue
BooleanValue = aListBox.HasHorizontalScrollbar

New in 2019r2

Supported for all project types and targets.

If True, adds a horizontal scrollbar to the ListBox.


The horizontal scrollbar only appears if the sum of the widths of the columns exceeds the width of the ListBox itself. If the widths of the columns is less than (or matches) the width of the ListBox, then no horizontal scrollbar appears.

The position of the thumb is indicated by ScrollPositionX. It is used to scroll the ListBox horizontally without a separate Scrollbar control.