the problem: coming back to a VI just to add another similar articulation, e.g. a marimba patch, you have to reopen the whole library tree.
solution:
1. do not collapse the library tree after a VI is closed. Each instance should remember and keep the library tree state as it had been left.
2. an option to specify a different tree root, independently for each VI instance, so for example, your viola VI would display only Viola articulation structure.
3. add a "locate in library" function, so that if you already have a patch in a matrix, it would reveal and jump to its location in the tree.
4. a proper search function -- say I want to see all available "violin tremolo" articulations, be it solo, chamber, orchestra or appassionata. or all "bowed percussion" or "scrapes", which would have to search on the sample level (or using tags).
(just to give proper credit, most of these features are included in NI Kontakt's browser)