Sometimes you might want to share data between multiple sites using a shared database of content, for example. Super can load any subpage onto a site, but not pages that are outside of the homepage hierarchy in Notion. This presents a problem as the shared database can only be a subpage of one of the sites.
But there is a workaround that can allow you to share the database - and that is to nest the sites.
How to nest sites to share data
Just say you want to have two sites, Site 1 and Site 2, and these will share a common database.
In Notion, make Site 2 a subpage of Site 1, and make sure that the shared database is also a subpage of Site 2 somewhere.
Site 1 will have access to everything in the Site 2 hierarchy.
If you need to hide Site 2 on Site 1, then hide the subpage on the new site using CSS.