Supporting IMGUI
Use the IMGUIContainer to place IMGUI code inside of a VisualElement. Everything you can normally do inside of OnGUI() is supported.
You can arrange multiple IMGUIContainer and lay them out by mixing GUILayout and UI(User Interface) Allows a user to interact with your application. More info
See in Glossary Toolkit layouts. Note that it is not possible to add VisualElement instances inside of an IMGUIContainer.
IMGUIContainer example- 2018–11–02 Page amended