MV - YEP_OptionsCore - add option to control game variable.

Before you write something stupid - I know well that you cannot game variables outside actuall game (except using dev console). But I'm struggling how to add to Options Core entry to control gameVariable's value via slider like to change window color tone.

Here's some entries that fails to do the thing.
Draw Option Code

Code:

var rect = this.itemRectForText(index);
var statusWidth = this.statusWidth();
var titleWidth = rect.width - statusWidth;
this.resetTextColor();
this.changePaintOpacity(this.isCommandEnabled(index));
this.drawOptionsName(index);
var value = this.getConfigValue(symbol);
var rate = ((value) / 6).clamp(0, 1);
if (value > 6) {
  var gaugeColor1 = this.textColor(14);
  var gaugeColor2 = this.textColor(6);
} else {
  var gaugeColor1 = this.textColor(20);
  var gaugeColor2 = this.textColor(21);
}
this.drawOptionsGauge(index, rate, gaugeColor1, gaugeColor2);
this.drawText("$soulrender.difficultyLevelLabel()", titleWidth, rect.y, statusWidth, 'center');

Process OK code

Code:

var index = this.index();
var symbol = this.commandSymbol(index);
var value = this.getConfigValue(symbol);
value += 1;
if (value > 6) value = 1;
value = value.clamp(1, 6);
this.changeValue(symbol, value);
$gameVariables.setValue(42, value);

Cursor Right Code

Code:

var index = this.index();
var symbol = this.commandSymbol(index);
var value = this.getConfigValue(symbol);
value += 1;
value = value.clamp(1, 6);
$gameVariables.setValue(42, value);

Cursor Left Code

Code:

var index = this.index();
var symbol = this.commandSymbol(index);
var value = this.getConfigValue(symbol);
value -= 1;
value = value.clamp(1, 6);
$gameVariables.setValue(42, value);

This entries are causing this error: