Using horizontal scrolling is very easy, even if multiple columns are used. The ScrollbarHorizontal property is used to define the desired scroll bar.
Once all items have been added to the tree control, the RecalcHorizontalExtent method must be used to allow the control to determine the optimal horizontal scrolling extent, which is determined by column widths and the contents of the the last displayed column.

The HorizontalOffsetChanged event occurs when the tree control is scrolled horizontally by the user.

Even if horizontal scroll bars are defined, RecalcHorizontalExtent must be used after all items have been added, otherwise the horizontal scroll bar will not be enabled or updated.