Some additional settings within WPSolr for filters that would be really nice to have:
Near “Select to display the facet as a tree” (under Show the hierarchy), it would be nice to have an additional setting to “Only display leaf categories with products” so that the only categories that would be displayed are categories with products (none of the parents).
In Algolia, this is the flat_heirarchy (flat_hierarchy_product_cat_str).
Further, it would be ideal to have another setting that allows us to utilize the non_flat_heirarchy (non_flat_hierarchy_product_cat_str) instead of the flat.
So to summarize:
1. The current (Display entire tree)
2. Display only leaves
3. Display Non-Flat
I would see people (maybe even myself) wanting to use a combination of these depending on what attributes they are dealing with.