Custom Objects for Dynamics GP 2016

Hi Dynamics GP Team,

I have found couple of links for the Class and Method Reference.

a) Class Reference: https://msdn.microsoft.com/en-us/library/cc533558.aspx

b) Method Reference: https://msdn.microsoft.com/en-us/library/cc508424.aspx

I want to know if the objectsmentioned in the Class reference link are customizable or not?

Also are there any Custom Objects available for GP 2016?

If it, is there any documentation available for this?

Regards,

Rajinder Singh