Can you add a hidden track before the first track of a CD using Toast Titanium?

No, Toast created Red Book CD audio discs that conform to the established standards, and cannot create a track before track 1. You can create a 'hidden' track by sticking extra content at the end of the last track with a suitable gap. Just insert a 5 or 10-second gap at the end of the last standard track and then the extra audio.