Add drop down selection to shipping method
I resolved the issue by adding a field to the order type and then instead of using
Order interface
$this-&gt;order-&gt;setData('field_omniva_parcel_machines', $val);

i used FieldableEntityInterfaces' set
$this-&gt;order-&gt;set('field_omniva_parcel_machines', $val);

and i accessed the value in the commerce-order-receipt.html.twig by using
      {% if order_entity.field_omniva_parcel_machines.value %}
         {{ order_entity.field_omniva_parcel_machines.value }}
      {% endif %}

Thanks again, Berry, for getting me started with this!