Sub-libraries (or library folders), for better organization of presets

This is intended for the content set filter (library browser):

My idea is that on mouseover, the icons can give you two options:
-Show the entire preset list belonging to that library in the search results, like it currently does
-Allow you to browse and pick a sub-library first.

One example of how this could be useful is the Halion Sonic SE library. It looks messy (see screenshot) and there’s no way show ALL Halion Sonic SE content using only the content set filter.

With sub-libraries/folders, it would be possible to have a single Halion Sonic SE icon.
Hovering over this icon would reveal two options (All | Browse…) . Clicking All would include all HS SE content in the search results, instead of just one part of the library. Clicking Browse reveals icons for the smaller portions of the library (Basic, Artist, Pro, Hybrid, TRIP). Alternatively, you could make it so clicking the icon always reveals all of its sub-libraries, and that also includes an extra icon that allows you to search for all of them together.

A few examples of how it could be useful for third party libraries with many presets:

-Libraries categorized by miking style (Like The Grand 3)
-Preset packs covering multiple Halion engines (Wavetable/Granular…)
-Electric piano library categorized by model (Rhodes Mark I, Wurly 200A…)
-Sampled synthesizers categorized by model (OB-Xa, Jupiter-6…)
-Electric guitars/basses categorized by effects (Dry/Effected/Amped)
-Separating experimental presets from the main library