Having an instrument loaded on a position (the snare position for example) - if you right click it in the drums tab, you'll get a list of all instruments of that type, from the selected library.
Say you have loaded a Slingerland from Superior Drummer 3 on the snare position. Right click the snare in the drums tab, and you'll see all snares from Superior Drummer 3, sorted by the different tools available.
There were some drawbacks of having a selection of tool on each instrument, so the current design was used instead.