[acdha]

1. As others have pointed out, you can change the style to alert

2. The system notification center (the icon on the upper right corner or a two-finger swipe from the right on a trackpad) lists every notification you haven't cancelled:

https://www.dropbox.com/s/q0o7gq7ndcbokin/Screenshot%202015-...

[tach4n]

As I said many hours before your comment; these solutions are clunky and limited compared to what's available to me on linux...