Changing the currency symbol; in MacOs preferences

You can not change the predefined currency symbols, but you can always create a custom format for your cells.

Create a custom cell format in Numbers on Mac - Apple Support (BW)

That could look like this

Currency information are not only used for display in a cell, they are also used for currency exchange calculation and the it would get difficult with self defined symbols.

Hope this will solve your question, please let me know if this worked for you or if something in unclear.

Ralf

Interestingly the Namibian dollar is not a choice of currency for me (US-English-$) even when I set the region of my Numbers file to Namibia. So I went to System Preferences and changed my currency from $ to Namibian Dollar and it shows it will be displayed as NAD, not $. Namibian dollar became a choice in Numbers and it displayed as NAD in the cell just like it says in System Preferences. Setting System Preferences back to $ put things back like they were, unable to choose NAD as a currency in a new document or any document that doesn't already have a cell formatted that way.

I think the difference is the region. For instance, the US dollar is $ if the region is US but in other regions it is US$. So if one's region is Namibia, the US dollar will be US$ and the Namibian dollar will be $, not NAD. Apple seems to think that the $ symbol is used for Namibian currency when in Namibia. I don't know if that is correct or not.

A possible answer to get around the problem in Numbers (but not system wide) might be to set the region of the document to something other than Namibia.