The issue I'm illustrating is purely the "Custom Paper Size" dialogue box. There are two custom paper size dialogues accessible within the printing/page setup that appear the same, but don't work exactly the same.

The image "Page Setup Manage Sizes.png" has additional functionality with the [+ v] button below the paper list. This dialogue however cannot reorder the paper size list (they seem to appear in a random order).

The image "Print Dialogue Manage Sizes.png" only has a [+] button that doesn't have a list attached to it. This dialogue seems to maintain an ordered list of custom paper.

Both dialogues show the same paper sizes as well, which seems to indicate one dialogue is a legacy one that hasn't been removed or updated. They both should have the same functionality.