Yes, this would be a great addition. Many downloads now include the booklet and liner notes, so it would be great to be able to access those on the Now Playing/Album Art page. The number of Roon subscribers who would benefit from this will increase with the advent of Quobuz Sublime and the option of downloads at reduced prices, which often include booklets or liner notes. Roon could add an additional icon to the row of icons at the top of the page for this purpose. And since the only icons that appear are those that apply to the album being played, if a Roon subscriber has no albums with notes or booklets, they would never see the icon at all. Those Roon subscribers with some albums with booklets would only see that icon in those cases.
As others have noted above, it would also be great if Roon moved that row of icons further down, to minimize the movement of a mouse. Either at the bottom of the section for album art, or in the very top of the white bar, and on the far right side, where there is plenty of empty space for that purpose.