Custom fields for tax details ?

Hello,

I got asked by my collegues if it is possible to add a custom field for tax details in the area marked on the screenshot :

Workcentar: Bussines Configuration - > Implementation Projects -> First Implementation -> Open Activity list-> Fine-Tune -> Tax on Goods and Services –> Define Tax Code

I think I found an object called ProductTaxationCharacteristics that should be extended. The object is in namespace: sap.com/xi/AP/FO/PriceAndTax/Globa but it is not listed as extendable

Now by everything I watched until now from the open sap course byd1 I think it should be possible. Problem is I am not sure what object I should extend to achieve what I need. Perhaps it has to do with business configuration ? Does anyone have any suggestions ?