yeah i think something very rené-esque could be done with grid where you would have 4x4 square of buttons on the left which would display the current value and allow you to change values by holding a button and turning the knob as you suggest, and on the right you’d have a 4x4 square displaying the current turtle position and pressing here would move the turtle to that position.
edit: as a starting point:
G.BTX 0 0 0 2 2 0 0 1 4 4
G.BTX 16 8 0 2 2 1 0 2 4 4
@F 0 0 3 3
set up buttons, one group will be on the left side - these are to set values (done by script 1), the other group is on the right - this is to jump the turtle to a position (done by script 2). also define the fence and the script for the turtle.
IF EZ G.BTNV: BREAK
X % G.BTNI 4; Y / G.BTNI 4
I SCALE 0 V 10 0 15 PARAM
PN X Y I
G.REC * X 2 * Y 2 2 2 I I
this will set the corresponding pattern value when a button in the left group is pressed. the knob value will be scaled to 0…16. we then draw a rectangle with the brightness set to the new value.
@X % G.BTNI 4; @Y / G.BTNI 4
this will set the turtle coordinates if a button in the right group is pressed, and it will display the current position by calling:
G.REC 8 0 8 8 0 0
G.REC * 2 @X * 2 @Y 2 2 1 15
this script will draw a rectangle corresponding to the current turtle position. this will also get called when the turtle itself moves to a different cell. this is where you probably want to output a trigger and update a CV.
this will also need a script to display the current values initially and to move the turtle (or set it up to move by itself).