In Splunk's Simple XML dashboards, token filters modify how token values are rendered. The |s token filter specifically wraps the token value in double quotes and escapes any internal quotation marks. This is particularly useful when constructing search strings that require quoted values.
For example, using $token_name|s$ ensures that the value of token_name is enclosed in double quotes, which is essential when the value contains spaces or special characters.
Reference:Token usage in dashboards - Splunk Documentation