You can create your own element with the predefined elements, and save it (as .fce file) for future usage. The customized elements can also have their own behavior, that means you can create some functional widgets. You can also pack multiple custom elements as a library.
All customized element have "custom" tag by default, so you can easily filtered them by clicking the "Custom" tag button:
Details of how to use custom elements can be found here.
You can download new custom elements and libraries from ForeUI store.