I am translating a short book I have written, and need a translation of "foreshadowed" which retains the connection with shadow, and not only the sense of "foretold".

I have thought of "antaŭmontrombrita" or "antaŭsignombrita". Would one of these work? Which one would probably work better? Is there a better option?

It is an important part of the translation: the title of the book is "A Foreshadowed Way".

I have thought of "antaŭmontrombrita" or "antaŭsignombrita".

I wouldn't understand what those mean. In trying to retain "shadow" you end up with an overly literal translation that doesn't really work in Esperanto.

I would probably use "aŭgurita" for this. So maybe "Aŭgurita Vojo".

The idea of "foreshadow" is that a future event casts a shadow on the present, so "to foreshadow..." means "to be a shadow of [future event]". Note that in English, to shadow usually means "to cast a shadow", but that figuratively it means "to be a shadow". In Esperanto, ombri is always "to cast a shadow", so antaŭombri must mean "cast a shadow on the past / in front", so the foreshadowing is an antaŭombro which is antaŭombrata by the future.

However, "foreshadowed way" seems to suggest that the road ahead is shadowy, and the present relatively sunny. Thus it is simultaneously ombra, ombrata (de arboj), kaj ombranta (la vidaĵon). Would you agree that the translation is antaŭombranta vojo?

Of course you can just say ombra vojo (antaŭe). It depends on the exact image.