The new Dataytype contectual menu has no effect with external tag provider.
is UDT implemented in 7.6.1rc1 for the RT external tag provider ??? 
No, sorry, UDTs did not make it in for 7.6. I know that we had talked about it, but unfortunately there were some issues that caused us to delay it.
It hasn’t been abandoned, but I don’t currently have a time line for it.
Regards,