[Enhancement] Hierarchy, custom columns, and user categories

[ownedbycats]

For convenience mostly, I sometimes group together related custom columns into user categories. Note that 'Fanfic Status' column and 'Status' category is identical items here:



However, the only way to have Calibre automatically add new items is the (somewhat hidden) option in Grouped Searches. This isn't the intended use and I don't think you can add it as a hierarchical sub-category.

So my suggestion, if technically feasible: The option to set 'All Items' into the user category, and let Calibre manage it.

Note that while 'Fanfic Status' is only a few items, the making of this post was triggered by me adding over 100+ items (all from the same column) to a different category.

This situation is a good part of the reasoning behind two of my enhancement requests: hiding items already added to the category (implemented) and being able to shift+click to select multiple items (not implemented).

Is this something other users would find useful?