Learn Spanish (Latin America): El simbolismo aquí es muy subjetivo; nadie sabe qué representa. - The symbolism here is very subjective; nobody knows what it represents.

Yes, you could say nadie sabe de qué se trata (nobody knows what it is about). Since we are discussing what the symbolism conveys or consists of, the impersonal tratarse de is a great alternative to representa. You would avoid the personal trata de here, as that would imply the symbolism is actively 'trying to' do something.

Why does qué have an accent mark in this sentence if it isn't a direct question?

Even though there are no question marks, the phrase nadie sabe qué representa contains an indirect question. The word qué (what) is representing the unknown information that nobody knows. It keeps its accent mark in indirect questions to distinguish it from the relative pronoun que (that/which).

If I wanted to explicitly say 'what it represents,' why shouldn't I add a pronoun like él or lo before representa?

In Spanish, subject pronouns for inanimate objects like el simbolismo are almost always omitted, so the 'it' is simply built into the verb representa. You wouldn't use él for a concept, and using lo would change the meaning to 'what represents it' because lo is a direct object pronoun, not a subject pronoun.

Is the suffix -ismo in simbolismo always spelled with an 's' in Spanish?