Filter only partially downloaded in library

[JoeloJoestar]

Describe your suggested feature

If I download some but not all the chapters of an entry, maybe because I temporarily want to read a few just to see if I like the manga, and then I want to find it back later on it's difficult because the Downloaded filter displays it together with those fully downloaded, making it hard to pick it up if I forgot which one was. Might it be possible to have a 4-state choice in the filter Downloaded (symbols in checkbox: + - ×) instead of implementing a new filter like Partially downloaded?

Other details

As an example, we can look at the logic behind the filters Unread and Started. I understand the usefulness of having both but just pointing out that the results overlap with each other in certain conditions, while for the single Downloaded filter there is an exclusion.

Acknowledgements

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