You can map any field of your customer from Shopify to Netsuite. Here is one basic example of mapping based on the fixed value. You can follow the same for your desired field.

• Select ‘Map Netsuite Field to Fixed Value’ in the ‘Operation’.
• Select the ‘Attribute type’ that is whether your field is custom or default. In our case it is a ‘Default Netsuite Field’.
• Select the name of your field from the ‘NS Field’ dropdown. Here we are mapping ‘subsidiary(RecordRef)’.
• Enter the field value of subsidiary(RecordRef) by simply inspecting that in your Netsuite.
• Click save.
  
  Note* – Same procedure follows for the custom fields in your Netsuite.