I built a language and UI around that way back, and many others have. I ditched mine because there were way too many unsolved problems I felt made it useless.
The problem is that if your primary means of working with the code is visual, the textual representation of your code then tends to be foreign to you when you're trying to use it to communicate aspects of the code, and when you constrain yourself to something that can be represented in a readable manner in a textual form, it turns out to be really hard to get to a point where the visual form is easier to work with.
E.g. something as basic as how you comment code in ways that roundtrips nicely is an unsolved problem.
If I have code represented as a graph, I'd be inclined to want to label relationships and dataflows that would be hard to place textually in a way that is meaningful in a textual version and that would roundtrip back to labels in the right place in the visual version.
I've not seen any attempts at visual code that gets even that right.
I've not managed to get it right myself either. If you force users to use an editor built into this tool, and edit a textual representation where some information is hidden, you can do better, but then if people e.g. copy a textual representation of the code into another application and back in, you end up with a mess.
Again, I want to be proven wrong about this. Badly. I love the idea. I've just seen enough failed attempts (and made enough failed attempts) to be disillusioned about it.