@Lindon so as a work around you can create a Faust based FX and drop it into a Hardcoded Fx slot, heres the faust code for a simple FM FX (as provided by Gemini):
import("stdfaust.lib");
// Modulator Controls
modFreq = hslider("Mod Frequency [unit:Hz]", 100, 10, 2000, 0.1);
modOctave = hslider("Mod Octave Offset", 0, -3, 3, 1);
modDepth = hslider("Mod Depth", 0.2, 0, 1, 0.001);
// Calculate the effective modulator frequency using the octave offset
effFreq = modFreq * ba.semi2ratio(modOctave * 12);
// Modulator oscillator (sine wave oscillating between -1 and 1)
modulator = os.osc(effFreq);
// Convert depth to a delay modulation amplitude (in samples)
// A small maximum delay (e.g., 2ms) keeps the FM effect tight and clean
maxDelayMs = 2;
maxDelaySamples = ma.SR * (maxDelayMs / 1000);
delayMod = (modulator * modDepth + 1) * (maxDelaySamples / 2);
// Apply Phase/Frequency Modulation using a fractional delay line
fmEffect(x) = de.fdelay(maxDelaySamples, delayMod, x);
// Process stereo or mono input
process = _,_ : fmEffect, fmEffect;