I'm not familiar with this but it seems more geared towards visually representing flow charts but it doesn't have the necessary verbosity for visual scripting. I might be wrong but I think this is only part of the puzzle. Can rules be defined such that, for example, a node port must be pointed to, or that a default value is available?
Besides the declaration of a graph, there also needs to be a way to define semantics, ie something akin to a Language Server Protocol. That way tooling can enforce validity while editing a graph.
It sounds like you're trying to make something new, in which case: I'd forego standardisation concerns for now, and focus on getting something that works, and where future prototyping can be backwards-compatible.
Besides the declaration of a graph, there also needs to be a way to define semantics, ie something akin to a Language Server Protocol. That way tooling can enforce validity while editing a graph.