Well first off they say it's a VST3 plugin which OpenMPT doesn't support, and even with using a VST3 <-> VST2 wrapper you wouldn't be able to get this functionality in OpenMPT:
- The VST2 API definitely has no features for drag&dropping MIDI between plugins and hosts.
- I'm not even sure how OpenMPT would implement this kind of feature if it was part of the VST3 specification. I mean, it should be clear that you cannot simply drag&drop MIDI notes into a tracker pattern. We could probably create a temporary MIDI file and load that, and then merge it into the current pattern. But there are a lot more things to take care of before this can happen.
