Thank you for dropping here in Community, @mumana.
 
I appreciate you for sharing for article and screenshots, you are making an effort in communicating with us.
I’m here to share some insight about the CSV file mapping in QuickBooks Online.

As of the moment, we cannot include corporate ID in importing a CSV file. Since it shows standard data and we should follow the correct format in uploading files into QuickBooks.

You can utilize this article for your reference regarding the CSV file in QuickBooks.
 
You can only add details reports limited to 3 custom fields on sales forms. Here’ how:

1.     Go to Settings ⚙, then select Custom fields.
2.     Select Add field.
3.     Enter a name in the Name field.
4.     Select the All Sales forms checkbox.
5.     If you want the custom field to appear on printed and delivered forms, turn on the Print on form switch. Otherwise, it will only be visible in QuickBooks.
6.     Select Save.
 

Moreover, refer to this article to know more about adding custom fields to the sales form and purchase order.
 

Let me know if you have queries, I’m always here to help you. Have a perfect day ahead!