You can build layouts using existing components. However, when you save the layout all the parameters and behavior of the components except the geometry are saved into the layout. This means that if you made modifications to the components in the layout, the original component files will not be updated. If you want to update the component files, you have to manually save each component. On the other hand, if you modify the behavior of an existing component that is used by multiple layouts, you have to manually delete the old versions of the component in the layouts and replace them with the new ones and configure them.
Ricardo Velez
Research and Development Manager