Generally, everything that goes into a story is symbolic of its theme. Of course a good story may be suggestive of implications that go beyond that theme, particularly if the audience extends the metaphors with which they have been presented. But in a simpler sense, symbolism as re-occurring imagery can keep the audience grounded in the fact that they are still within one story or a series of inter-related stories. The symbology provides bridging from event to event.

A story whose theme is about temptation might have an apple placed somewhere in the home of the people who are dealing with temptation. In another location someone might say the word "apple" or the characters might be offered apple juice or apple pie. At work they might use Apple computers. This sort of repetition can help the audience focus on how each piece of the story is related to each other piece, which is precisely what we are after in a free-form digital story.