A few decades ago, a high school student sent surveys to well known writers and asked them how conscious were they about symbolism and interpretation for what they were writing. The answers were varied and interesting.
Here’s my perspective as a fiction writer and editor. “Symbolism” is much too strong a word, but I would guess that most of my fiction writing friends would say that they are conscious of at least 95% of the resonances/imagery/parallels in their language and details. Sometimes you need to think this things out if only to keep things consistent. Suppose you were writing a story or novel with Christian overtones; you’d want to make sure that any imagery identified with Christianity (crosses, bread, wine, etc) be used consistently with the overall theme. Sometimes, writers go out of their way to make their imagery inconsistent or misleading or ironic if only to make things fun. Often storytellers like to write allegorically, so allegories definitely can be applied to many different situations. See for example all the crazy interpretations of Wizard of Oz. Poetry is a completely different matter because poets go out of their way to use words and phrases which have multiple meanings and resonances, leaving it to the reader to decide at what level the work ought to be grasped. Finally, the question itself seems to be an artefact of psychoanalysis, which heavily influenced that particular generation of writers. If you asked a bunch of writers the same questions today, I doubt that many of them would attribute such an important role to the “subconscious” for their writing.