Extend Sales Order in C4C

Hello all,

I am trying to extend an existing business object of Sales Order (using the extend BO functionality in Cloud Application Studio). However, I can't find it in the

Add New Item -> Business Object Extension -> Namespace. I checked all the namespaces in the mentioned path and am still unable to find Sales Order BO to extend.

Eagerly waiting for valuable inputs.

Best Regards,

Nikhil