Support for sub-entries?

[Blrp]

Multiple ebook files can already be grouped under one entry, but I'd like to see groups of sub-entries that can have different metadata in addition to the main entry's metadata. For example, versions of the same book - this would be especially useful if they have different titles.

You could also group an audiobook as the main entry together with its PDF supplement as a sub-entry. To that end, it would be useful to have support for sub-sub-entries.

Each sub-entry and sub-sub-entry would have its own row, but they'd be visually grouped together and act as one entry for sorting/search. Metadata fields for sub-entries can be filled or left empty or marked as inherited from the main entry. Each metadata field could have its own default behavior for new sub-entries: copied, empty or inherited.

An alternative view could be enabled which treats each sub-entry as separate, so e.g. you can search among just your audiobooks even if some of them are sub-entries that are grouped together with other formats. Also, while using the grouped view, a checkbox by the search box could be used to enable filtering out sub-entry rows even while the matching rows are still grouped.

Does this sound like a good idea? Is there anything like this already? Has it been discussed as a potential new feature?

[BetterRed]

I do something vaguely similar using calibre:// URL links in a custom long text column.

Books are cross-linked with a show-book, a book-details, and one or more view-book links. So it creates a network structure rather than a hierarchical structure which is what your 'grouping' scheme seems to imply.

I have pro-forma HTML snippets that I paste into a #links/Links long text custom column, e.g. :

<a href="calibre://show-book/_hex_-426f6f6b73/NNNN"><span style="color: #ffff00">Jump to release</span></a> ::: <a href="calibre://book-details/_hex_-426f6f6b73/NNNN"><span style="color: #ff55ff">Release details</span></a> ::: <a href="calibre://view-book/_hex_-426f6f6b73/NNNN/FORMAT"><span style="color: #00ff00">View FORMAT</span></a></p></div>

The "NNNN" gets replaced with the Book number (id), etc.

BR