The excalibur widget, which we use for the whiteboard, allows to add components from an external library:
https://libraries.excalidraw.com/?target=_blank&referrer=https%3A%2F%2Fapp.dev.flbi.net%2Fnotes&useHash=true&token=9lf0VUtGUS_wmBw1fTA7j&theme=dark&version=2&sort=default
However, the backlink doesn't work and it is not possible to add external elements into the library.
Either implement the backlink or turn off the library feature.