These suggestions would help immensely.

In addition, I'd like if the new category dropdown would remain on its selected category while we scroll through various level ranges. So, for instance, if we're looking for Woolen Yarn, we could set the category to cloth and just scroll up/down the left-hand column's level ranges list, seeing only the few cloth items for each level range. Currently, it keeps resetting back to "All" every time we switch levels, so to see the cloth items, it's a cumbersome pattern of selecting one level range, moving to the center column so we can select the Cloth category, then if it's not there moving to the left column to select another level range then back to the center column to restore the Cloth category setting we were looking for, and so on through each level range until we find our item.

(To enable that change, the category drop-down would probably need to be updated to show all item types made by that crafting class, rather than just the categories that exist at the given range (as it has now). So for some categories, you might occasionally see an empty list with just a "no items of the selected category" message.)