Sometimes, especially after iOS/iPadOS upgrades, Notebooks may indicate that a huge number of documents needs to be synchronized. As a side effect, and due to the nature of iCloud sync, Notebooks may become slow or fail to display documents. This

With an active iCloud account, Notebooks can store your documents on iCloud and automatically synchronize them to all connected devices. When set up this way, Notebooks uses a predefined folder on iCloud Drive (iCloud Drive/Notebooks), so you should not create that folder yourself.