Does anyone know if I can use the enriching data to set macros  that can then be used as kv-parser options.

These values might change on a message by message basis.

For example:

parser p_kv {

    kv-parser (

        prefix("$kv_prefix")
        value-separator("$kv_vseparator")

        pair-separator("$kv_pseparator")

    );