For me i'd like use some visible notation to mark the important paper, recently, i have found that via changing the color of the tags, a color block could appear at the head of the paper's title in the paper library window. But that's not enough for me. The color to be selected is few and less information is carried by the color blocks. I suppose that if we can choose a figure of the paper manuuly as the cover of the paper in the library window, the efficience of searching paper will be promoted greatly.