Hi Andrew,
It is possible to create/edit tax codes in the Fine Tuning activity 'Tax on Goods and Services' if the project is not set to live.
Currently, there is no default tax content like tax type, tax rate for country French Polynesia provided by SAP. Hence, it is not possible to create tax codes for French Polynesia without this content.
It is possible to create tax content for countries like French Polynesia which does not have any default content through SAP By Design Studio.
Also, we planned to provide default content for French Polynesia and will reach the systems as per the release.
Regards,
Vijay Kumar