So how about making it possible to set sources in the waveform editor to modulate frequency, phase or amplitude (FM, PM, and RM) of another source? Could be a modifier where one can pick the source and set the amount. Like, we already can turn the waveform into a phase modulator for sine carrier.
Summary
This would greatly benefit from having individual setting for normalizing and removing DC for every source.
Edit: the normalizing and removing DC seem to affect the combined waveform so the above hidden text isn’t an issue after all.