This would be tabs as apart of a World that link to whole new projects that are still apart of the main 'idea'/world. Eg, say your World was Lego Adventurers. The main World/project page would be 'Adventurers', this page would give an overview of the World and perhaps some main/recurring characters etc. Then there would be subproject tabs, eg Egypt, Jungle, which would lead to pages that are the same as the current project page, with tabs for characters, places, transport etc. etc. This would allow world builders to make their worlds larger and more detailed, especially when creating multiple storylines or episodes.