Most (all?) of the plug-ins have a bank of 8 presets, on the right-hand side of the GUI, labelled A to H.
Now, these are not available as a plug-in automation parameter. But you can select any of them by sending a MIDI Program Change message to the plug-in.
Or, if you want to select from more than 8 presets, you can put a bunch of the plug-in's presets into a particular folder and select any of them from there using a PC message. Click [MIDI] then the "Preset switch" tab and look at "Program change in presets".




