Basic group effects question

Exactly.

on init

make_perfview
set_script_title("FX")
set_ui_height_px(350)
  declare const $SK_SLOT := 0
  declare const $FX := -1
  declare const $GROUP := 0

    declare $i := 0 { a variable to count each while loop }
    declare const $MAX_GROUPS := 11 { the absolute number of groups }

  declare ui_knob $RotatorKnob (0,1000000,1)
  set_knob_unit($RotatorKnob,$KNOB_UNIT_PERCENT)
  set_knob_defval($RotatorKnob,500000)
  make_persistent($RotatorKnob)
  set_knob_label($RotatorKnob,get_engine_par_disp($ENGINE_PAR_RT_SPEED,$GROUP,$SK_SLOT,$FX))
end on

on ui_control ($RotatorKnob)
  $i := 0
  while ($i < $MAX_GROUPS)
    set_engine_par($ENGINE_PAR_RT_SPEED,$RotatorKnob, $i ,$SK_SLOT,$FX)
    inc($i)
  end while
  { the above loop will set groups from 0 to 10. it may seem confusing because MAX_GROUPS = 10
    but remember that group IDs are zero based, so if you have 11 groups and want to
    change the settings in all groups, you will be setting engine parameters for groups 0 to 10 }

  set_knob_label($RotatorKnob,get_engine_par_disp($ENGINE_PAR_RT_SPEED,$GROUP,$SK_SLOT,$FX))
end on

from the above you can derive further ideas.