Is there a symbol for “and/or”?

There is a symbol for it in predicate logic.

"And/or" is just called "or" and is represented as ∨, from the Latin vel meaning or. But note that it's a separate symbol from the letter "v", though similar.

In contrast, "or" in the sense of "this one or that one but never both" is called "exclusive or" or "xor" and can be symbolized as ⊻ or ⊕.

Also, in programming you might see "and/or" represented as | or as ||, and "xor" represented as ^. Which confusingly looks a lot like ∧, used in logic to mean "and".

The virgule is used only when indicating a line break in an inline quotation.

There is no symbol for "and/or" likely because in technical or scientific realms "or" means "just A, just B, or both A and B." Restated, "or" in technical realms is inclusive. "Exclusive or" or "xor" (pronounced eks-or) means only "just A or just B."