How a collection's user interface is split between the file list and the preview (Split Direction).
public enum PdfCollectionSplitDirection
ISO 32000-2 §12.3.5, Table 158 (PDF 2.0).
kind:method, kind:property, kind:ctor. Press Esc to clear.HorizontalSplit horizontally (H).NoneNot split (N): the file list only.VerticalSplit vertically (V).