This class represents the collection split dictionary. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 158, page 450.

Adobe Supplement to the ISO 32000, BaseVersion: 1.7, ExtensionLevel: 3; Table: 8.6b, page 31.

System.Object
    WebSupergoo.ABCpdf14.Elements.Element
       WebSupergoo.ABCpdf14.Elements.CollectionSplitElement

A collection split dictionary describes how the portfolio panel is divided between the file list and a preview or detail pane. The Direction entry selects horizontal or vertical splitting. The Position entry gives the split location as a fraction of total size.