Some vendors create their plugin presets as .vstpreset files for VST3 or AU plugins. One such example is Plugin Alliance plugins. When you host in the MPH such plugins, upon loading the third party plugin the MPH will search under:

Mac /Users/USER/Library/Audio/Presets

Win C:\Users\USER\Documents\VST3 Presets\

the folder with the plugin’s vendor name (ie Plugin Alliance) and within that, the folder with the name of the plugin loaded and it will display these vstpreset files in the menu on the controller’s window. 

When a plugin with VST3 Presets is loaded the MPH will automatically display a button on the top encoder row named “VST3 Presets”. This button brings up a list with the available VST3 Presets of the hosted plugin.

Alternatively, to view and load VST3 Presets: Right click > Presets > VST3 Presets

From that list you can choose any preset and it will be automatically loaded in the hosted plugin.