Hi @Corine, thanks a lot for the update. Ok, so this does seem to be related to the Wish list item: Sharing/copying pages, elements, symbols, components, etc across projects - Product feedback - Forum | Webflow, which addresses the need to be able to copy elements from one site, to another site hosted in Webflow.
At the moment, it is not possible to copy those, it would be needed to recreate the page on the second site. I wish I could give you a better solution at the moment. I will be there cheering with you when the feature is added!