Flex Builder renders any visible custom components (components that inherit from UIComponent) in the MXML editor's Design mode. You can double-click a custom component in the layout to open its file and edit it.

1. Open an MXML file that uses a custom component.
2. In Design mode, double-click a custom component in the layout.

   The component file opens in the editor.

You can also right-click a custom component to display the context menu and select Open Custom Component.

1. Edit the custom component.

Distributing custom components

Distribute custom components by creating library projects. For more information, see About library projects.