@Adcirruserp
Steve's suggestion above should work for this scenario.
You can extend SPTemplateItemProcessor and override SaveBucketImport.
The Shopify tags are already available in the imported external product object (bucket.Product?.Extern?.Tags), so you can process them after the standard import and create/update the corresponding Sales Category assignments.
For example, the customization point would be:
[PXOverride]
public async Task SaveBucketImport(SPTemplateItemEntityBucket bucket,
IMappedEntity existing,string operation,
CancellationToken cancellationToken, SaveBucketImportDelegate baseMethod)
{
// Read tags from bucket.Product?.Extern.Tags
// Map tags to Acumatica Sales Categories
// Create/update category assignments
await baseMethod(bucket, existing, operation, cancellationToken);
}
Hope this helps!