When a component is created inside Library it is added under MY COMPONENTS.
The Library ToolBox can be crowded with lots of components designed in the Library. In order to reduce the number of components displayed in the toolbox, it is possible to select the Show in ToolBox property.
This feature becomes handy when a component is no longer going to be added to another component. Such as a FlexLayout for SliderDrawer, will be used once only. There is no need to display it in Library ToolBox. Or a component will be used several times as a child of another library component. After designing the main outer component there is no need to display the child component in the Library ToolBox.