That depends on the used layout, because each theme is structured differently.
To remove the Orbit/marquee wheel in layout Robospin, open layout.nut:
serach for :
local wheel_r = [ 30, 25, 20, 15, 10, 5, 0, -10, -15, -20, -25, -30, ];
local num_arts = 8;
change to:
local wheel_r = [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ];
local num_arts = 2;