#EditorGUISplitView
EditorGUISplitView is an utility view that allows you to easily add a split view with draggable resize functionality to your Editor Windows.
It couldn't be easier to use
EditorGUISplitView horizontalSplitView = new EditorGUISplitView (EditorGUISplitView.Direction.Horizontal);
EditorGUISplitView verticalSplitView = new EditorGUISplitView (EditorGUISplitView.Direction.Vertical);
public void OnGUI ()
{
horizontalSplitView.BeginSplitView ();
DrawView1 ();
horizontalSplitView.Split ();
verticalSplitView.BeginSplitView ();
DrawView2 ();
verticalSplitView.Split ();
DrawView2 ();
verticalSplitView.EndSplitView ();
horizontalSplitView.EndSplitView ();
Repaint();
}