Apps like Safari and Notes support multiple windows per app. The documentation only shows two ways to switch between these windows:
From an open app: In the Dock, tap the app you want to view.
Swipe up from the bottom edge of the screen if you don’t see the Dock.
From the Home Screen: Touch and hold the app you want to view, then tap Show All Windows.
For an app in the Dock, swipe up from the bottom edge of the screen if you don’t see the Dock.
Is there a keyboard shortcut, like how Cmd-Tab switches between different applications? macOS has Cmd-`, but it doesn’t work on iPadOS.