Can Trick Shot be used to add a die to Snap Shot?

At its core the question is: does adding an attack die count as modifying attack die?

Yes, for the same fact that Jan ors, fenn rau, and mauler mithel all increase the amount rolled

Adding a die result (which does imply the addition of an actual die, just one already set to the desired result) is a kind of dice modification. Altering the number of dice you roll is not.

Hell of a trick shot to get a R1 obstructed shot, though not impossible.