So, I figured out how to do this.
First, terminology. I’m naming this stuff 'cause I couldn’t find it in the user guides. Doesn’t mean it’s not there, I just couldn’t find it.
VST Wrapper - called this because it’s different in every host (I’ve tried so far). This is the header and footer that the Plugin Editor’s UI is wrapped in.
Preset List Dropdown - In the header, preset names with Program Change Numbers.
Options Menu - the triple stripe thingy at the far right of the header.
Procedure - select an empty Preset slot in the Preset List Dropdown
select a preset in the plugin
click on the selected Preset slot again
in the Options Menu click Rename Program, type in preset name - not necessary for it to work, but how
else to know which slots are assigned?
The Preset name now appears in the Preset List Dropdown, and can be selected with a MIDI controller.
You need to make a binding from the properly routed controller to the plugin with a Program Change event and for the Target Control “Select Preset Indexed”.
This works the charm with BIAS AMP. Unfortunately, the Thermionik plugins don’t appear as a target for routing from the MIDI controller. You can do it if you put the plugin in an embedded rack but, since each of the 25 amps is a separate plugin, any MIDI sent to the rack affects ALL of them, and I don’t know if I want to deal with setting up 25 separate embedded racks!
Only problems left - when you send MIDI to the BIAS controls (vol, tone, etc) with a rotary controller (I use a Korg nanoKontrol) all of the controls jump when you make the first adjustment after opening the plugin editor. I suspect that this is Positive Grid’s problem, as it doesn’t happen with any of my better sims (Amplitube, S-Gear, Guitar Rig, TH3).
Also, when changing presets, sometimes an audible “BEEP” is heard. Again, not an issue with the other sims, BUT - the others I mentioned handle their preset switching internally - using Cantabile’s preset selection process is not required. So maybe this could be a Cantabile problem?
BTW - you can get a free DEMO version of BIAS AMP Desktop Version, works fine, just has an audio cutout every so often to remind you it’s a demo.