I noticed in the VST3 version of my plug-in (and the Juce Demo Plug) that master bypass control doesn't show up as automatable, whereas it does for AU, AAX and VST2. I added Vst::ParameterInfo::kCanAutomate to the bypass paramter flags in the VST3_Wrapper and now this is consistent with the other plug-in formats.
info.flags = Vst::ParameterInfo::kIsBypass|Vst::ParameterInfo::kCanAutomate;
Anyhow, I was thinking this would be a good thing to change directly in Juce. What do you think?