Hi Sunny,
Once a custom voice has been made and assigned to a position in the Custom Bank it can be post-edited in Voice Set and Mixing Console, respond to Pitch Bend etc. just like any other voice.
The ref. manual page 17 describes how to import a wav file to make a normal voice (not drums- they start at p.22).

Page 19 covers assignment to keys for normal voices.

Page 20 covers how to use Voice set to apply the usual editing parameters to the voice.
(As I said above you can also post-edit like other voice types, once assigned to the Custom Bank and loaded into R1,2,3 or Left.)

John