UGS module issue

Recently, I’d like to modify the UGS UI and the cutsom the sycn category.
But there contains both in C++ and C# program.
I’d like to know the function about this two parts. What about there relationship?
How to transport the data or call function between c++ and c#, if they work together.

The UI is define by C# program or the SlateUGS module?
I read the source code find they both define the same structure or function without dll import/export, which make me confuse.

And the category contains in workspace.cpp but the official document say it was defined in workspace.cs


here is the ducument about the UnrealGameSync customly sync categories.