Combinig Keboard shortcuts

Is there a way of combining say Shift+D and P or Shift +D and FF etc. so they can be assigned to a keyboard shortcut and therefore assigned to a single button on a midi keyboard controller?

Yes, but not from within Dorico itself. Keyboard Maestro, AutoHotKey, Metagrid, Stream Deck and many other apps that I’m not familiar with can all do this.