Passing additional parameters with signup form

Hello there,

I am integrating the Klaviyo form with Shopify. I have a requirement where I have to pass an additional parameter with the form. But I tried many ways and it is not working, the parameter is not going through. Could some one help me fix this.

The additional parameter I am passing here is bmi_results.

{%- form 'customer', id: 'bmi-email', class: 'form' -%}
        <div class="">
          <p>Vul je emailadres in om jouw BMI score te ontvangen</p>

          <div class="input">
            <input
              type="email"
              id="bmi[{{ section.id }}][contact][email]"
              name="contact[email]"
              class="input__field"
              required
            >
            <label for="bmi[{{ section.id }}][contact][email]" class="input__label">
              {{- 'general.newsletter.email' | t -}}
            </label>
          </div>

          <div class="input">
            <input type="hidden" name="contact[tags]" value="bmi-calculator"/>
            <input type="radio" name="bmi_result" id="bmi_results" value="100" checked/>

            <input type="hidden" name="$fields" value="EmailInterests,EmailFrequency,bmi_result" />
            <input type="hidden" name="$list_fields" value="EmailInterests" />

            <div class="consent-selection" style="margin-bottom: 10px;">
              <label>
                <input type="checkbox" name="consent" required>
                <span
                  >Ik ga akkoord met de <a href="/policies/privacy-policy"><b>privacy verklaring</b></a></span
                >
              </label>
            </div>
            <button id="sendEmail" type="submit" is="loader-button" class="button button--primary">
              {{ section.settings.send_button_text }}
            </button>
          </div>
        </div>
      {% endform %}