Modulators!

I wonder whether the problem I posted here is related

When you try and add a modulator to Groove Agent - it only really shows the QC equivalents in the drop down list of parameters. It doesn’t show any of the deeper parameters like you would see on other VST e.g. Frequency cutoff on a VST synth can be modulated. However it does (kind of) let you use the Learn function - but in a buggy way ?