Is there any data structure called Proxy Graph which has practical implementation? I tried to search for it but didn't any sources, so I want to know if any such data structure or concept exists.
If you understand the word "Proxy", you may have a clue about "Proxy Graph".
First, let me clear your confusion. Proxy Graph is not a data structure, although you might have a Graph data structure to represent, store and implement Proxy Graph.
When dealing with large "Topographic Maps", the proxy graph contact model approximates by using the "proxy location to vertices and edges". If you are dealing with computational models, you may have to look for optimal data structures for graphs and that might depend on what you are trying to accomplish.