Sorry to hear they are impossible - although, being a programmer myself, I find it hard to believe that displaying an entered page number is impossible - after all, it could be a simple as simulating the appropriate number of "next" or "previous" button clicks.
In any case, I also wanted this feature so I could quickly find collectibles that I have not yet collected as well. I do use the features of the collection window as you suggest, but that only works if I actually have the collection
