The client needs to have a different order type for orders passed thru Shopify from TikTok. An Order Data field, Source Name, is populated with ‘TikTok’. A different Acumatica Sales Order Type is required because TikTok takes care of the reporting of sales taxes so Tax Calculation needs to be disabled. The normal Shopify Orders are only taxed in two states and the client has Avalara.
The Expression Editor only can be used for the External fields.