Brad, I am testing 3620 with various VST3 plugins and most of it goes ok. Pretty exciting you’re getting this done!
I may have found a small bug/issue:
I was constructing a new linked rack to serve as a “Master Bus”, where I put Waves C6 stereo (VST3) and Izotope Ozone Elements (VST3) on it. Works all fine. But after saving it, exiting Cantabile, starting Cantabile again and loading the song with the linked rack in it, C6 “failed”, and it removed the input routing. (see picture)
I redid this several times, and it happens consistently.
If I replace the C6-VST3 with C6-VST2 it works fine
Maybe not your highest priority right now, but perhaps you can address this at some point.
By the way: still today (2nd October) Izotope Ozone Elements is free of charge! It’s good, so get it!
https://www.izotope.com/en/products/ozone.html