Hi,
I think that the browser doesn't really work and one of the reasons is that it's too difficult to quickly get to the result you want. Scrolling up and down while navigating a tree structure is not appropriate for the tangled web that is music styles, instruments, ...
Almost ever major software instrument and effect has moved away from this and is using a tag-based approach. Omnisphere being the best example of this, but Native Instrument's one might suit the Pico best. For instance Kore 2 (http://www.native-instruments.com/uploads/pics/03_fast_and_easy_access.png). I can imagine that alongside the 'mode' status, the Pico can be set in 'browse status' when you press any key that does browsing (pressing an active key afterwards might send you back to controlling browsing what already in the panel). When in browse status, the keys on the Pico basically toggle tags on and off, allowing you to very quickly narrow down the selection that you want. Which tags are present are of course context sensitive and change based on what you're selecting. The right panel would then contain the list of items that match the selected tags.
Instead of using the scroll keys, I would using the strip controller to move up and down as I think it would feel more natural. Making a selection could be done by using one the octave keys.
What do you think?
Geert