Pioneer V8000 - Manual (Page 92)

Internal Registers
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9.2 Function User Setting
Function assignment for No1 through 30 can be changed by user in advanced set up.
The procedure is given below for an example of GROUP 3 setting change to “MENU”.
Open ADV SETUP and switch EXTEND TERMINAL to User and press Enter.
And then the following window opens.
DOWN button to select "GROUP 3"