Change decimal notation in SU01

Hello,

Could you please share the method to change the decimal notation in SU01 under Default Tab->Decimal Notation or

System -->User Profile-->own data -->Defaults tab-->Decimal Notation to 3 digit decimal. i.e 12345.678

By default I can see three different types of decimal notation. I need to manually add a new decimal notation with 3 digit in place. i.e 12345.678

I don't want to make any changes in OY04 t-code, if we make any changes in INR currency, then our complete HR related salary structure get change. Please share the steps to add custom decimal notation without making any changes in OY04.

Regards,

Arjun