That is exactly the same feature just another name for it. As such this can be closed as duplicate of it. Oh, I see, it has already been done! 👍

A watchlist and favourites are two different things. A watchlist item will notify the user of changes whilst a favourite item is just a bookmark to items of interest. Additionally, favourites, in a good implementation, allows categorisation and organisation, whilst a watchlist is just an unorganised list of items. A watchlist is not a good substitute for favourites.