If I am not mistaken, it used to be possible to prioritize a series, such as a set of commentaries, by sorting the Library by Series and then dragging the whole series to the Prioritize list. This handy feature seems to have been lost in one of the upgrades. I realize that you can right click on one of the books in the series and select Prioritize this Series. But I find dragging the whole group was much simpler and quicker.