Adding parameters post launch to a plugin?

[jpo]

Not sure if that is directly relevant to the issue here, but the AU code from Apple does not respect parameter ordering when using param ids, as explained here:

AU Parameter Order

In a plugin I have whose params are not inheriting AudioProcessorParameter the parameters order is the same in AU and VST. But in plugins using AudioProcessorParameterWithID, the order is different in the AU indeed. This is because the JUCE AU Wrapper calls AUScopeElement::UseIndexedParameters (numParams) when you use legacy parameters. Apparently the Apple audiounit code stores the parameter list in a std::map when using paramID instead of indexes. And its GetParameterList implementation is: …

In my opinion it is a bug. By applying the patch I suggest there, I think Logic can handle addition of new params as long a they appended at the end of the list, and not inserted in the middle of the param list – I have not tested this particular case, though, but I’ve been using that patch since then.