I am exactly in the same situation. Trailblazer’s Intricate Gossamer Insignia does not appear in the window for the mystic forge.
However, It works with Viper’s Intricate Gossamer Insignia, which is also a new one and the recipe can be bought to a vendor in HoT.
That’s why I also think that they forgot to add it to the forge. Hope they’ll do it soon…