Hello,
paladin181: You are notified. and when you click on your library, you will have to refresh once, then click on the "My Collection" button and display "Updated" to see them (It sometimes doesn't work before a refresh, there are no updated items to display).
Either I do not get your point at what browsing in the Library or how to "refresh" it, either mine does not work as expected. I remember having had a few update notifications in my library over the past year. But they later vanished before I did any download of the updates. These notifications never returned and I found no way to make them show up again.
Moreover, I have no more than one game with a changelog available (Lovers in a dangerous space). Nothing coherent with the few update notifications I got for sure in the past for other games.
Updates management at GoG looks like a mess, at least from the user's point of view.