On what platforms does that work? I have a love-hate relationship with PD. It seems really horrible (usability wise) compared to the much more refined MaxMSP but that latter doesn’t let you make plugins.
Max used to have a tool called Pluggo. I believe that it was removed as part of the deal with Ableton and M4L. If they had kept Pluggo, then all those M4L devices would be instantly available for any host.
I’ve just played around loading a few patches: midi only, midi to audio, audio to audio.
All worked ok, with patch saved in the plugin state as far as I can tell.
One patch referenced other pd files, which worked when I first loaded the main pd file in GP (it referenced the other files ok), but didn’t work after save/close/re-open of GP.
I haven’t read any documentation yet, just started experimenting.
I made a stereo delay with 3 parameters (delay time, feedback and level).
Rackspace is attached, if anyone has downloaded the plugin and wants to test. I used VST3.