@Christoph-Hart Makes sense, I investigated more about having multiple MainController's and it was definitely the wrong route. Pretty satisfied with FRONTEND_IS_PLUGIN for my use-case.
Thanks!

Note that I had to disable the pool "search mode" when loading the same sample over a range of MIDI notes, otherwise updating the start/end positions would be mirrored on every sample.

auto pool = sampler->getSampleMap()->getCurrentSamplePool(); jassert(pool); pool->setDeactivatePoolSearch(true);

I believe this is why this pool mode exists, @Christoph-Hart, i.e.: to allow each duplicate sample entry to have its own properties?

E.

@Christoph-Hart Hi! Thanks for the quick reply. Yeah, that's what I came down to, I'll base64 encode my properties to avoid adding a child ValueTree. That'll work even though it's not really optimal.