Right click on the EQ and enable the spectrum analyser

You can set the properties for it in your script.
const dsb = Synth.getDisplayBufferSource("parametricEq0");
inline function setEqProperties()
{
local props = {
"BufferLength": 4096,
"WindowType": "Blackman Harris",
"DecibelRange": [-90.0, 18.0],
"UsePeakDecay": false,
"UseDecibelScale": true,
"YGamma": 0.2,
"Decay": 0.6,
"UseLogarithmicFreqAxis": true
};
local dp = dsb.getDisplayBuffer(0);
dp.setRingBufferProperties(props);
}
