Does the favourites feature only work with email sign-in, or can it function without a user profile? Additionally, if cookies are not cleared, will the saved items remain visible?
The favorites feature usually requires users to log in. That’s because the data for favorites is stored in a user-specific column, so the app needs to identify who’s currently logged in to save and show the right favorites for each person.
As Javieri said, favorites usually require a user-specific column. For public users, those columns’ values are reset every time the app is closed.