So I'm going to let the Symbolism portion of this discussion be its own thread, in case others want to contribute. Here, I wish to start a thread about how characters' actions signal themes to readers and define personalities, arcs, and themes.
My writing professor (like many) always said "show, don't tell.". He felt audiences could infer much from action without needing description to spell it out. My favourite example has always been "he held the door for the elderly woman with the groceries" versus "he was nice.". One sentence creates a scene you can picture, and define for yourself what his character is like. The other declares it, leaving less up to the reader.
Small actions can tell you as much about a person as a big one. I'm going to use Disney movies for references because they are very mainstream - most people know them so there won't be much in the way of spoilers. Plus their basis in fairy tales makes them heavy on traditional, known symbols, and plots are straightforward. Other examples can go into nuances later.
Ariel the Little Mermaid shows her inquisitive, adventurous and independent character by collecting human things - which leads inevitably to conflict with her father because that's against the rules. Her character as a person won't leave it at that - she has to push limits, explore boundaries. So Triton's adamance about rules leads to Ariel going to the sea witch, and turning human. The whole plot occurs because of their personality traits.
Likewise in the beginning of Mulan - she is a lateral thinker who comes up with unique solutions to problems, as evidenced by setting up a puppy to chase a bone and drag chickenfeed around the yard. She struggles with the traditional roles of her culture but ultimately uses her problem solving skills to replace her father in the army, succeed at training camp and defeat the Huns. The seeds of that ability are shown in her early scene speeding up the chore of feeding chickens.
The themes of the Little Mermaid and Mulan both have to do with the individual finding the place they belong, because they are different from their environs.
Harry Potter (not Disney but well-known) gets a lot of description - The Boy who Lived and the Chosen One. But the first action that really shows his character is with the Sorting Hat - choosing not to be Slytherin. The Hat recognizes his courage and his desire to take the harder road of "good" over the easy road to success through evil. Throughout the series he chooses the right path over temptation, starting with the Philosopher's Stone in the Mirror of Erised. Dumbeldore states the theme of. The series after the death of Cedric Diggory - "the choice is coming between what is easy and what is right.". Harry lives out that choice constantly.
These small actions are early indicators of the bigger picture. They define the characters and the roles they will play in the story.
Do your characters show seeds that blossom into personality traits? What relationship does that have with the themes of your story?