It's so ridiculous that this isn't a standard thing in all samplers, preset selectors, osc wave selectors... whatever. From the days of MIDI, Juno 106, DX-7, RX-5, TR-808... you name it... they ALL HAVE prev/next buttons. It is as fundamental as note C is. it is how the music is done, you first 'pilot' record some idea with any sound and then you hit prev/next buttons until you are satisfied with it. If you first try to look for the right sound, you loose so much time that the idea you had in the first place is no more there in your head/fingers to record it.
Maybe a drop down menu like in Reaverb would work. This way you could arrow to the prev and next, and easily go to another file in the same folder if you know what you want to try next and it's not coming up soon.
--------------------- ten awatar to na jaja jak coś [br]