I just decided to add a custom column to one of my libraries tracking the page count - my first custom column - and noticed that a "Custom metadata" section now takes up about half the space in the metadata editor (using the "All on 1 tab" layout). Now I don't actually care about editing my page_count column from the metadata editor, so I have deselected it in preferences:
However, it would appear that regardless of this, the large section still appears in the metadata editor:
This section cannot be resized, since the border between "Basic metadata" and "Custom metadata" is not draggable. I can only make the "Cover" section larger, which doesn't help me at all. I have a lot of books with long titles so this large "Custom metadata" section is completely in the way.
In the first place I don't think it makes any sense that this section appears even though it's completely empty because I deselected the one custom column in preferences. But I would at least like to resize this empty section so that it doesn't take up so much space.