abstract ボタンを押すと概要が表示されます。
Favorites は唐突に無効化されるかもしれません。飾りだと思ってください。

Pro Tip! You can use the following shortcuts to quickly navigate through papers (All of them work even when the Quickview is open)

←, → Move between cards    space Open/Close Quickview     esc Close Quickview     enter Open the paper's page     f Add a paper to Favorites